10 northern european mysteries abound, and the veil of the unknown still hangs over many puzzling events across the region. Whether it’s a baffling homicide, an inexplicable natural phenomenon, or a historic enigma, the answers often stay hidden.
10 Northern European Mysteries Overview
10 Double Murder In Linkoping
On the afternoon of 19 October 2004, residents of Linköping, Sweden, witnessed a shocking scene: Anna‑Lena Svensson, 56, was suddenly stabbed in the abdomen on a busy street, while nearby eight‑year‑old Mohammed Ammouri let out a terrified scream before collapsing. The boy died instantly; the woman survived long enough to reach a hospital, where she succumbed a few days later.
Investigators gathered the murder weapon – a butterfly knife – and a fragment of clothing, and initially believed they could pinpoint the culprit within a day, focusing on a suspect believed to be mentally unstable. Yet, fourteen years on, more than 7,000 individuals have been questioned, and the killer remains at large, with no clear motive emerging from the evidence.
9 Purple Slime In Lyngen Fjord
In August 2015, fishermen operating off northern Norway’s Lyngen Fjord reported a bizarre, violet‑coloured gelatinous mass that seemed to materialise overnight, blanketing millions of cubic metres of water.
Scientists who examined the phenomenon likened the slime’s consistency to margarine and initially suspected it originated from decaying jellyfish. The substance clung to caught fish and even interfered with sonar equipment, prompting experts to note they had never encountered such a purple ooze in the fjords before.
Nearly three years later, no definitive source has been confirmed, and the true nature of the mysterious slime remains an unanswered question.
8 Where’s Beverina Castle?
Latvian chronicles recount that in 1208 Estonian forces assaulted Beverina Castle in the Trikata district, only to retreat for the night beside a lake near the road to Beverina. Crusaders and the local leader Kaupo later discovered them there, drove them away, and then shared a morning meal at the same lake.
The castle itself is referenced sixteen times in the Chronicle of Henry as the residence of Talivaldis, yet its precise location has never been recorded. Archaeologists suspect it may lie on two hillocks near Lake Vaidava, but no systematic excavation has yet been undertaken to verify this theory.
7 What Happened To Greenland’s Vikings?
In September 1408, Sigrid Bjornsdottir and Thorstein Olafsson were wed in a granite‑lined church on a Greenlandic fjord after their vessel was blown off course from Norway to Iceland. They settled among the long‑standing Viking community, and their marriage is documented in three contemporary letters.
When European explorers returned to Greenland in the 18th century, they found only abandoned settlements. The prevailing explanation cites a cooling climate that eroded arable land and timber, but newer research suggests the Black Death may have forced the Norse to abandon the island, leaving the true cause of their disappearance still debated.
6 Swedish Spheres
In May 1808, residents of Biskopsberga, Sweden, observed the sky dimming unexpectedly, allowing them to look directly at the sun. From the west, a series of dark, spherical objects drifted toward the dimming disc, aligning themselves in a straight line as they approached the horizon.
One sphere struck the ground, leaving behind a delicate, cobweb‑like film that vanished shortly after. The phenomenon persisted, with the spheres continuously moving eastward before disappearing, and no scientific explanation has yet been offered for this extraordinary aerial display.
5 Ulfberht Swords
Among Viking artifacts, the Ulfberht sword stands out for its remarkable metallurgical quality. By 2014, archaeologists had uncovered 170 examples dating from AD 800‑1000, each featuring a blade of exceptional purity.
While contemporary European swords were often brittle and impurity‑laden, Ulfberht blades contain almost no contaminants and boast a carbon content three times higher than typical medieval steel, rivaling modern alloys. The origin of the raw material remains a mystery, as large‑scale steel production did not emerge in Europe until centuries later.
Adding to the intrigue, each sword bears the inscription “ULFBERH+T,” the meaning and purpose of which continue to puzzle scholars.
4 Murder Of Auli Kylikki Saari
On 17 May 1953, 17‑year‑old Auli Kyllikki Saari of Finland rode her bicycle to church, where she worked in the office and attended prayer meetings. After returning home that evening, she claimed to be tired and retired to her bedroom—an unusual statement that raised concern among her parents.
Later that day, Auli left again for a prayer gathering with her friend Maiju. Witnesses reported Auli appearing nervous throughout the day. After parting ways at a crossroads, a passerby named Tie‑Jaska saw her walking alone for another 1.6 km. Subsequent weeks yielded reports of a cream‑colored car with a bicycle in its trunk and alleged cries and gunshots near Kaarankajarvi lake.
In July, her bicycle was discovered deep in a forest, and by October, her body was recovered near the spot where she was last seen, accompanied by a scarf, a man’s sock, and a shoe, with her coat draped over her head. Despite numerous suspects—including a vicar, a police officer, and a ditch‑digger—no one has ever been convicted, leaving the murder unresolved.
3 Denmark’s Ancient Labyrinth
In early 2017, archaeologists uncovered a massive Stone Age labyrinth in Stevns, Denmark. The structure consists of five concentric rows of fence, each featuring entrances offset from those in the other rows, a design choice whose purpose remains unclear.
Excavations have revealed pits containing fragments of tools, pottery, and axe heads, yet these finds have not clarified the labyrinth’s function. Some scholars propose it served as a sun‑worship temple, with rituals performed within its winding pathways, but further investigation is required to confirm any theory.
2 Kaali Crater Mystery
Over 7,000 years ago, a sizeable meteorite entered Earth’s atmosphere and fragmented, with several pieces striking Saaremaa’s Kaali region in Estonia, creating a field of nine craters that persist today.
The largest crater is encircled by a Bronze‑Age stone wall, presumed to have been erected by an ancient cult that may have used the water‑filled basin for ritual purposes. Animal bones discovered within the enclosure suggest possible sacrificial activities, yet researchers cannot fully explore the lake’s depths because oak deposits restrict diving to a mere four metres.
1 Scandinavian Star Fire
On 7 April 1990, a catastrophic blaze erupted aboard the passenger ferry Scandinavian Star, which plied routes between Oslo and Denmark. The inferno spread rapidly, claiming 159 lives, exacerbated by thick smoke that obscured exits and a multilingual crew unable to effectively direct passengers to safety.
Initial investigations suggested a single arsonist, but a 2009 probe concluded that multiple individuals would have been required to ignite the fire. In 2016, a retired ship inspector accused two unnamed crew members of deliberately setting the blaze, pledging to testify in court.
However, a 2017 inquest found no concrete evidence of sabotage or financially motivated arson, leaving the true cause of the tragedy unresolved and the responsible parties at large.