Crypts contain more than just human remains. These subterranean skeleton sanctuaries hold secrets. Artistic masterpieces, relics, and even evidence of disease have been recovered from crypts. These mysterious artifacts tantalize archaeologists with the window they provide into the deceased’s world. Many more enigmas await discovery in the shadows of crypts.

10 Siberian Death Masks

In 2015, researchers found 20 death masks in an ancient crypt in Siberia’s Kemerovo region. The tomb belonged to the enigmatic Tashtyk people, warriors who controlled large portions of Siberia between 300 BC and AD 500. The crypt was dug into the ground, surrounded by a stone wall, and covered with a log roof. The massive burial pit took two years to excavate.

Archaeologists discovered the remains of 30 people who had been cremated and placed inside dummy bodies made of fabric and leather. “Death masks” of gypsum provided the dummies’ faces. Some were surprised to find that the Tashtyk death masks have stereotypically European features. The remains of children were discovered outside the tomb. None of the youngsters had death masks.

Gypsum is a soft mineral, so many of the masks are in fragments. However, experts believe they may be able to piece together the broken faces.

9 Seven Magical Mummies

In 2009, archaeologists discovered seven mummies in a 900-year-old crypt with walls covered in magical inscriptions. The naturally preserved remains came from deep within a monastery in Old Dongola, the capital of the medieval kingdom of Makuria in modern-day Sudan. The crypt contained the remains of seven males, all over age 40. The burial chamber was sealed with bricks and mud mortar.

Black ink inscriptions in Sahidic Coptic and Greek cloak the crypt’s whitewashed walls. There are Gospel excerpts along with magical names and symbols, which are believed to have been intended to protect the dead from malicious forces. Tradition held that the recently deceased were in a state of flux and were vulnerable before they faced judgment.

The crypt was first located in 1933, but excavations would not occur until over 70 years later. Experts believe one of the mummies might be Archbishop Georgios, one of the most powerful Christians in Makuria.

8 The Buddha’s Skull

Archaeologists believe they may have found a piece of the Buddha’s skull in a 1,000-year-old chest discovered in a crypt beneath Grand Bao’en Temple in Nanjing, China. The stupa not only contained what might be the skull of the Buddha, but it was filled with the bones of other Buddhist saints. The box was constructed of carved sandalwood, covered in silver and gold, and encrusted with crystal, glass, lapis lazuli, and agate. Inscriptions reveal that the stupa was made during Emperor Zhenzong’s reign (AD 997–1022) during the Song Dynasty.

The stupa was nestled within an iron box, which in turn was housed in a stone chest. According to tradition, when the Buddha was cremated, King Ashoka of India decided to divide the saint’s body into 84,000 equal shares. China received 19 of these, including the Buddha’s parietal bone. The remains were originally housed in another temple, which was destroyed in warfare 1,400 years ago.

7 Cancer Mummy

In 1995, archaeologists unearthed an 18th-century Hungarian mummy that is revolutionizing the study of cancer. The naturally preserved remains were discovered in the sealed crypt of a Dominican church in Vac. Roughly 260 mummified remains were found in total. A team of Israeli researchers tested the corpses to see if they were carriers of cancer-causing genes. In one individual, they discovered a mutation in the APC gene, which is known to cause an increased risk of colon cancer.

What the findings suggest is that a predisposition existed before the disease became a serious health issue. Today, colorectal cancer is the third most common form of cancer. Most consider it to be a modern disease that results from a lack of activity, processed foods, and a longer life expectancy. The presence of the mutated gene in other mummies would indicate that genetic inheritance might be even more important than environment.

6 Secret Medici Crypt

In 2004, archaeologists discovered a secret crypt belonging to Italy’s powerful Medici family. During an earlier exploration of a known Medici crypt, experts were shocked to discover that the grave of the last Medici, Grand Duke Gian Gastone, was empty. In an attempt to find the missing corpse, they discovered a clandestine chamber behind the main altar of Florence’s Church of San Lorenzo. Researchers lifted a stone slab to reveal steps leading to the hidden crypt.

The secret chamber contained one adult coffin, which held Gastone, and eight child coffins. All of the children’s bones showed signs of rickets. This is likely due to a lack of vitamin D in their diet. Being sheltered indoors under thick, pale makeup didn’t help their absorption of this necessary element. Researchers cannot identify some of the dead youngsters. It is likely that at least some of them are illegitimate children.

5 Earliest Depiction Of Jesus

In an Egyptian crypt, archaeologists recently unearthed what might be the oldest depiction of Jesus. Located in the ancient city of Oxyrhynchus, the mysterious underground structure could only be accessed once researchers removed 45 tons of stone. The walls of the crypt contained six layers of paint. The last was from the period of the early Coptic Christians.

One painting drew experts’ attention: The mysterious image shows a tunic-clad young man with curly hair performing a blessing. Some believe this is the earliest known likeness of Christ. However, until researchers translate cryptic inscriptions around the figure, the man’s identity remains a mystery. The crypt belongs to a 17-year-old scribe and a family of priests.

Archaeologists report that they haven’t had time yet to explore another mysterious space attached to the crypt. They have no idea what they will find in the new hidden chamber.

4 Crypt Of The Ancient Astronaut

The secret opening to the crypt of Pakal II, the Maya ruler of Palenque, was discovered in 1948. It took four more years to clear the rubble away so that researchers could enter the hidden chamber. The monarch’s remains were discovered clad in a jade mask with beads. Sculptures and carvings of Mayan underworld beliefs surround the ancient ruler.

Pakal II supposedly died at age 80. However, the skeletal remains appear to be that of a 40-year-old. What’s more, a carving on the lid of his tomb has convinced some that Pakal II might not even have been human. The engraving became famous after the controversial 1968 bestseller Chariots of the Gods suggested that, if turned sideways, the image depicts Pakal II aboard a spacecraft. One viewer may see Mayan iconography related to death, rebirth, and the cosmos. Another sees a fuselage, complete with a breathing apparatus and controls.

3 Prague’s Hidden Masterpiece

Art historians recently discovered a never-before-seen monument deep within Prague’s Loreto crypt, beneath the Church of the Nativity of Our Lord. The walls of the tomb are covered with intricate depictions of death, resurrection, and allegories for time. Dated to 1664, these amazing depictions of Ars moriendi utilize only black and gray to create a sophisticated shading system known as chiaroscuro.

The paintings were discovered in 2011, when the crypt was opened for the first time in decades. Many of the works are inspired by Dutch art, including copies of Rembrandt. The identity of the artist remains a mystery. Some speculate that it might have been Cosmas of Austria or Viennese painter Tobias Pock. Both had a history of working with the Capuchin monks. It is also unknown whether the subject matter was selected by the artist or the crypt’s patron, Countess Elisabeth Apollonia of Kolowrat.

2 Heart Burial

In 2015, archaeologists unearthed five 400-year-old hearts from the crypt under the Convent of the Jacobins in Rennes, France. The embalmed organs were buried in heart-shaped lead urns, which feature inscriptions revealing ownership details. Dated to the 16th and 17th centuries, these preserved pumps were discovered by teams inspecting the convent before it becomes a conference center. They are part of a long tradition of “heart burials.”

The hearts were cleaned and removed of embalming material so that they could be analyzed with MRI and CT technology to get a glimpse into ancient circulation. One heart had no disease, while three others showed serious blockages, including plaque and atherosclerosis.

Researchers discovered a knight’s heart inside the grave of Louise de Quengo, Lady of Brefeillac. It belonged to her husband, Toussaint Perrien. The practice of being buried with the heart of one’s spouse was common during this period.

1 Jesus’s Family

In 1980, archaeologists discovered a hidden crypt in Jerusalem. The Talpiot Tomb contained ten mysterious ossuaries. Some claim these boxes, meant for holding human remains, are definitive proof that this was the final resting place of Jesus of Nazareth and his family. This discovery meant that Christ not only was not raised from the dead, but had a wife and children.

Inscriptions on the ossuaries reveal them to belong to “Jesus, Son of Joseph,” “Mary, the master,” and even “Judas, son of Jesus.” Some have been lead to believe that this means Christ, Mary Magdalene, and their son.

Some critics argue, however, that the name “Jesus” is actually “Hanun.” Others believe the inscription on Mary’s ossuary has been mistranslated and should read “Mariam and Mara.” They believe this ossuary contains the remains of two females. In addition, the inscription on Mary’s ossuary is in Greek, while the others are in Aramaic.

Abraham Rinquist is the executive director of the Winooski, Vermont, branch of the Helen Hartness Flanders Folklore Society. He is the coauthor of Codex Exotica and Song-Catcher: The Adventures of Blackwater Jukebox.

There’s something about an underground tunnel that I personally love. It’s dark, spooky, full of spiders and low-hanging pipes—and sometimes, there are dead people. It’s romantic and educational! (I was not the average thrill-seeker as a child, okay?)

When I think of crypts, catacombs, and underground cities, I jump to antiquity first. There are the necropolis under the Vatican Basilica and the burial crypts of ancient Egypt. Don’t forget the famous Catacombs in Paris and Palermo. By definition, a crypt is a “chamber, such as a vault, wholly or partly underground especially: a vault under the main floor of a church.” It makes sense we would associate crypts and underground cities of bones with our European counterparts and ancient ancestors. It’s not something we think could exist under our feet in cities in the U.S. like Boston, New York, or even Seattle.

So here’s a look at some of the American crypts and subterranean cities you can visit (and I recommend it) if you’re into winding tunnels, mystery, history, and sometimes just centuries-old dead guys. No judgment here.

Related: 10 Bone-Chilling Facts About the Catacombs of Paris

10 Seattle, WA

Believe it or not, Seattle, Washington, has an entire secret underground city that burned down in a large fire in 1889. The new city was simply rebuilt on top of the old ruins, which are still open to tours today. Between 1890 and 1907, the old ground floor continued to be used. Merchants either carried on business on the bottom floors that had managed to survive the fire or the new above-ground layer. Pedestrians then used the now-underground levels with sidewalks lit by the pavement lights above.

As you can imagine, the Underground level led to the seedier businesses. In 1907, the city condemned the Underground out of fear of the bubonic plague that was spreading along the West Coast at the time. Underground Seattle became abandoned and left to deteriorate and for use as storage. All the new abandoned space under the city became tempting accommodations for vagrants, illegal gambling, prostitution, opium dens, and speakeasies.

Today, you can visit the Seattle Underground on one of many tours. There are still artifacts and relics down there from decades past. It’s creepy and supposedly haunted, as most underground cities reportedly are.^[1]

9 New York, NY

If a more somber tour of a crypt is your thing, I would recommend popping over to New York City. Right off Mulberry Street, you’ll find St. Patrick’s Old Cathedral, with the only active Roman Catholic cemetery in Manhattan outside its doors. Some of the inhabitants are over 200 years old. The cathedral itself was the largest in the United States when it was completed in 1815, and it was the seat of the first Bishop of the Diocese of New York. Much of the wooden cathedral interior burned to the ground in 1866 in a fire set off by a kitchen stove.

Step inside today and walk down into the basement, however, and you can take a “candlelight” (It’s an LED flashlight, you know, because of the fire) tour of the crypt beneath the church. You won’t see any visible bones, but you will see lined hallways with ornate vaults and notable inhabitants. There’s Countess Annie Leary, the Delmonico family, and “Honest John” Kelly, to name a few. Oh, and upstairs, you’ll see where Francis Ford Coppola filmed the baptism scene in The Godfather.^[2]

8 Indianapolis, IN

Indiana is not a place where you’d think an underground catacomb tunnel network would exist, but it does. And it so happens that it’s very creepy to behold if you’re by yourself. Trust me on this one.

In 1886, the city of Indianapolis constructed two public buildings on Market Street designed by architect Dietrich Bohlen. These buildings were: City Market and Tomlinson Hall. City Market remains a thriving and beloved part of the downtown community of Indianapolis. Tomlinson Hall, however, disappeared from the cityscape in January 1958 when a fire ravaged the area. The city took down the remains later that year.

Today only its iconic arch and basement, known as the Catacombs, mark this once vibrant space. You can tour the catacombs as well! According to the city, the Catacombs qualify as both a ruin and a redevelopment opportunity, and they welcome visitors to explore the city’s past, present, and future. They have gone on record to say that Indianapolis’s Catacombs don’t contain bones or crypts (that they know of) but rather scores of brick barrel-vaulted arches. Nonetheless, it’s a cool space to visit if you get the chance. If you do find bones, high tail it out of there.^[3]

7 Atlanta, GA

Let’s talk about The Crypt of Civilization at Oglethorpe University. You’ve probably never heard about it unless you were really into the Guinness Book of World Records in the early ’90s or lived in Atlanta at some point. So, for background, I grew up in Atlanta and once went on a field trip to Oglethorpe University, where I saw The Crypt of Civilization. As a 10-year-old kid, I was intrigued and invested in opening this crypt and pretty much have been ever since.

There are no bodies (we think) inside this crypt. They also claim there are no valuables, gold, or jewelry inside this crypt. So, what is it? Very few facts exist about The Crypt itself. According to the University, “The Crypt of Civilization at Oglethorpe is the oldest millennial time capsule in conception and the largest in the world. In 1936, detailed plans were executed to build an extraordinary time capsule—one designed to store records for over 6,000 years, done on what could perhaps be described as an epic scale never before conceived. The visionary of this improbable quest was Oglethorpe University president Dr. Thornwell Jacobs, who has been called ‘the father of the modern time capsule.’” Jacobs was convinced that his generation could be the first to perform what he later called “our archaeological duty.” This was an obligation to provide for future historians “a thorough and accurate record, scientifically selected and preserved, of life in the twentieth century.” Some more facts to include:

• The Crypt of Civilization was sealed on May 28, 1940
• It is not to be opened until May 28, 8113
• No, you can not go inside; but you can visit the sealed stainless steel door

A lot has changed in the world since 1940. Oglethorpe has access to a lot of human archaeological archives. What’s in this crypt? Your guess is as good as mine. We’ll have to wait until National Treasure 3 or the end of the world to find this one out. I recommend going to look at the door if you’re in town. It’s as ominous and mysterious as you’d think.^[4]

6 Waterbury, CT

This is the only catacomb I’m truly scared of. Holy Land, USA is a religious “theme park” in Waterbury, CT, and nothing really says fun for the family like getting tetanus or succumbing to a deteriorating cave-in.

The park was originally opened in 1955 by John Baptist Greco, a totally normal lawyer, but it closed to the public in 1984 and was subsequently vandalized. It was also the site of the rape and murder of a 16-year-old girl in 2010. It was subsequently purchased by a local non-profit and reopened on September 14, 2014, with an inaugural Mass and access to ruins of the grounds. So, what’s the story about the catacombs here?

At the height of the park’s popularity, there was once an attraction called “Catacombs: A History of the Church.” But it now serves as a stark warning of the deterioration of the space. According to a local review: “Any foray into these ancient burial chambers would likely end with a slip down a hidden staircase with your forehead impaled on a plank of rusty nails.” Nope.

Originally, it ran about 200 feet along the old parking lot in a series of corridors. Viewed from the parking lot, it appears to be underground but is actually all above the surface. On the far end, a small entrance contains a sign: “The Pictorial Life of Christ—From the Cradle to the Cross.” Another crudely hand-lettered sign lists every pope up to 1978. The area is open to the public during daylight hours. I would not recommend tempting your fate and going after hours. There are plans to reopen the park in its former glory. ^[5]

5 Cincinnati, OH

Cincinnati has a lot of old European architecture engrained into the heart of the city, from the restaurants to apartments and even down to where it buries its dead. It’s not often that a group of families comes together to request their long-dead relatives remain buried together. But that’s exactly what happened at Over-the-Rhine’s St. Francis Seraph Church. The original church was called Christ Church and was built in April of 1819 by the first Catholics of Cincinnati. In March 1822, Edward Fenwick, first bishop of Cincinnati, took possession of Christ Church as his cathedral. Later that year, the new bishop had Christ Church moved to a location downtown.

The cemetery remained while the city grew up around it. In November 1858, the cornerstone was laid for the present St. Francis Seraph Church. The remaining bodies were entombed in a crypt, Poets’ Corner–style , below the altar of the new church, which was consecrated on December 18, 1859.

There they stayed for more than 100 years, inaccessible to everyone except the inhabitants of the friary, which remained cloistered until the 1970s. Now, thanks to the American Legacy Queen City Underground Tour, you can see the crypt in person.^[6]

4 Newark, NJ

In 1937, Father Mateo Amoros was working as the assistant pastor at St. Joseph’s Church in Newark, New Jersey. Father Amoros reportedly took a trip to Montreal that same year, saw some catacombs, and decided that his church should also have them. The problem? The state of New Jersey generally frowned upon opening a new burial chamber beneath the church and told him no. However, Father Amoros had a much grander (and, honestly, creepier) vision in mind for his catacomb.

Instead of human remains, he would have wax corpses of saints and martyrs. By doing this, he opened America’s first wax museum, and you can still visit this “crypt” today. You can see some of the greatest hits, including St. Tarsicio, a 12-year-old altar boy who was beaten to death for refusing to surrender his Eucharist. Also, St. Genaro, who was “thrown into a lighted oven” and “thrown in with wild beasts” for choosing Christianity over paganism. Nearby lies St. Ines, “obedient girl and role model,” who refused to marry a Roman—she said she was already married to God. She then escaped vengeful murder because she was a virgin. So she was dragged to a brothel, deflowered, and then vengefully murdered.^[7]

By the way, this catacomb was also listed on a site as a top place to visit for Catholic field trips. Lovely!

3 Columbia, SC

You can’t buy a ticket to tour the Columbia catacombs, but if you’re brave enough, you can see the mysterious tunnels that all the residents know about. However, no one has an explanation for why they really exist.

“Elaborate brick arches. A two-century-old phenomenon. Cypress floors. Confederate gold. Beautifully crafted brickwork. Underground architectural wonder. Clandestine passageways for state officials. Part of the Underground Railroad.” These phrases include some of what Columbia residents use to describe and explain the tunnels. Built in the 1800s, their original purpose remains a mystery.

Chris Robinson, a professor at USC, has visited and written about the catacombs extensively. He’s even taken artifacts in hopes of finding answers as to why they’re there. So far, no bodies have been found, but the tunnels are miles long—as long as they are ornate. If you’re the adventuring type, go see for yourself and try to answer the centuries-old mystery.^[8]

2 Washington, DC

D.C. has a little bit of everything. You can drop by the White House and try to catch a glimpse of the sitting President, grab some food over at Ben’s Chili Bowl, and even visit the truly breathtaking catacombs and gardens at the Franciscan Monastery. Wait, what?

Built in the late 1800s and early 1900s, the Franciscan Monastery served as a place for Americans to go when travel to the Holy Land was difficult. Exploring the catacombs makes visiting the monastery feel like a unique adventure, unlike a typical trip to a museum. The designers of the monastery even traveled to the Holy Land and consulted travelers to capture every detail. They wanted a visit to the Franciscan Monastery to feel as authentic as possible. And since the 1920s, the catacombs have been home to the bones of a young child, Saint Innocent, the martyr, that came from the Catacomb of St. Callistus.^[9]

1 Boston, MA

If you’ve been to Boston, you’ve probably stopped by the Old North Church. At the very least, you’ve heard the story of Paul Revere making his famous ride. It’s a rite of passage living in America, I think. What you probably didn’t know is that the Old North Church has a very elaborate crypt underneath it, and there’s plenty of space if you still want to be buried there today. It’s a lot cheaper than you’d think, and you don’t even need to kick out the dusty neighbors. (However, you would have to be cremated!)

Old North Church houses in its basement a crypt containing approximately 1,100 burials. From 1732 to 1860, the church interred congregants below its very floorboards. Since the church has plenty of space beneath and little space above ground, they decided to make the most of what they had to meet the burial demands of the congregation. In the basement, 37 separate brick vaults comprise the tombs in each of which 20 to 40 full coffins could be deposited.

The crypt tour is dark, dusty, and full of history, as you’d probably expect. If you’re tall, you’ll have to watch out for those low-hanging pipes. You’ll be able to see an open vault with an 18th-century coffin still intact. There might even be a ghost or two lingering around, but what else do you expect for the city where it started?^[10]