Surtr Cave — also known as the Cave of Surt — is a lava tube in Iceland whose cavernous interior has been associated with Viking-age ritual activity since Norse settlers first arrived on the island. The cave takes its name from Surtr, the fire giant of Norse mythology who is said to engulf the world in flames during the apocalyptic battle of Ragnarok. Inside, explorers encounter a massive man-made stone wall that guide Kevin Smith describes on camera as standing approximately 3.5 feet high, 4.5 feet wide, with its top reaching roughly 15 feet above the original cave floor and spanning some 30 feet in width — reportedly one of the largest man-made constructions known from Viking-age Iceland. Beyond that wall, the collapsed section of the lava tube is littered with an estimated 750,000 animal bone fragments, believed by researchers to be the remnants of ritual offerings rather than ordinary food waste. The cave sits in Iceland's volcanic landscape, a setting that made an immediate impression on Gates: as he notes in the episode, the Norse conception of a fire-breathing underworld may itself have been shaped by settlers watching volcanic eruptions on what was quite literally their doorstep.
Norse settlers arrive in Iceland; volcanic activity in the region likely encountered within the first decades of settlement, according to Gates' guide on camera
Cave believed to have been used for ritual activity, based on the constructed stone wall and large accumulation of animal bone fragments
Gates investigates Surtr Cave during Expedition Unknown Season 4, Episode 2, 'Vikings in America'
On camera, guide Kevin Smith walks Gates through the mythological and physical significance of the cave, drawing a direct line between Iceland's volcanic landscape and the Norse fire cosmology. Smith suggests that the very concept of Surtr — the world-ending fire giant — may have been 'born here,' shaped by settlers who watched eruptions unfold around them shortly after arriving. Gates echoes the idea that this 'whole notion of Norse fire gods was kind of born here... a product of sitting on their front porch, watching the world end.' While Smith is Gates' primary on-camera source in this segment, the episode frames him as a knowledgeable local guide rather than a credentialed archaeologist, so his interpretations should be understood in that context.
The archaeological evidence from Surtr Cave is genuinely striking by any standard. The constructed stone wall — massive by Viking-age construction norms — suggests intentional, organized activity inside the cave rather than casual habitation. The approximately 750,000 unburned animal bone fragments found beyond the wall are particularly significant: the absence of burning points away from cooking or feasting and toward ritual deposition, a pattern archaeologists associate with ceremonial offerings in Norse-period sites across Scandinavia and the North Atlantic.
What remains genuinely debated, based on available information, is the precise nature of that ritual activity. Was the wall a boundary marker separating sacred space from profane? A containment structure? A monument? Without dated stratigraphic excavation data provided in the episode, the timeline and purpose of the wall remain open questions. Similarly, while 750,000 bone fragments is a staggering number, the species, depositional sequence, and chronology of those bones would be key to understanding what ceremonies — if any — took place here.
Gates' episode places Surtr Cave within the broader 'Vikings in America' narrative of Season 4, using it as context for Norse cosmology and the mindset of Viking-age Icelanders. The episode raises the right questions — Is the wall a boundary? Were the bones offerings? — without claiming to resolve them, which is an honest reflection of where the archaeology appears to stand.
The stone wall inside Surtr Cave is described on camera as one of the largest man-made constructions known from Viking-age Iceland, with its top reportedly reaching 15 feet above the original cave floor.
An estimated 750,000 animal bone fragments have been found inside the cave — the sheer volume, combined with the absence of burn marks, leads researchers to favor ritual deposition over ordinary food refuse as an explanation.
Surtr (also spelled Surt) is the Norse fire giant prophesied to wield a flaming sword and set the world ablaze during Ragnarok — a myth that Gates' guide suggests may have been directly inspired by Iceland's volcanic eruptions.
Iceland's first Norse settlers are believed to have arrived around c. 870 AD, and volcanic eruptions likely occurred within their first decades on the island — a cataclysmic backdrop that may have shaped their mythology in real time.
Surtr Cave is believed to be accessible in Iceland's volcanic interior, though visitors should check current local advisories and conditions before attempting to explore any lava tube, as these environments can be unstable and require appropriate gear. Helmets are recommended — as Gates' guide notes wryly on camera, they're 'just there to protect your dental records.' Guided tours with local experts familiar with the cave are strongly advisable.
Reykjavik is the nearest major city, located approximately 50–60 km to the southwest based on the site's coordinates, though exact distances should be verified locally.
Summer months (June through August) generally offer the most accessible weather and longest daylight hours for cave exploration in Iceland. Winter visits are possible but require extra preparation given Iceland's extreme conditions.
Scandinavia
Scandinavia is the homeland of the Norse settlers who named and used Surtr Cave, and Gates' broader Viking investigations connect Icelandic sites to Scandinavian culture and mythology.
La Garma Cave
La Garma Cave is another prehistoric cave site Gates investigates where the underground space itself appears to have held ceremonial or ritual significance for ancient peoples.
Tayos Cave
Tayos Cave is a similarly dramatic subterranean site Gates explored where archaeological mystery and large-scale underground formations intersect with questions about ancient human activity.