Prasat Pram — sometimes rendered as 'Prasat Thom' or simply the 'Koh Ker Pyramid' — is believed to be the largest stepped pyramid at the remote archaeological complex of Koh Ker in northern Cambodia, and is considered among the tallest pyramidal structures in all of Southeast Asia. Rising in a series of massive terraced tiers, the pyramid dominates the jungle landscape of what was, for a brief period in the early 10th century, the capital of the mighty Khmer Empire. Inscriptions at the site suggest that a towering golden linga — a sacred Hindu symbol of divine power, estimated at roughly 15 feet in height — once stood at the pyramid's summit, though its current whereabouts remain unknown. At the pyramid's heart lies a roughly 50-foot central shaft, adding to the structure's air of mystery and making it a focal point for archaeologists trying to understand both the monument's original ritual function and the fate of its most sacred object. Gates came here for Season 12 of Expedition Unknown to investigate what caused Koh Ker's mysterious and rapid decline as a capital city — and to search for clues about that missing golden linga.
Koh Ker briefly established as capital of the Khmer Empire under King Jayavarman IV; Prasat Pram pyramid constructed as the symbolic center of his new power base
Capital believed to have shifted back toward the Angkor region under Jayavarman IV's successors, leaving Koh Ker largely abandoned
Josh Gates investigates the pyramid in Expedition Unknown S12E07, climbing to the summit and descending into the central shaft in search of answers about the lost golden linga and the city's downfall
On camera, Gates consults journalist and Cambodia specialist Nick Ray — who he credits with literally writing the Lonely Planet guide to Cambodia — for context on what makes Koh Ker so puzzling. Ray frames the pyramid as a 'temple mountain,' meant to be 'home of the gods,' and notes that in the early 10th century it represented the largest structure the ancient Khmers had built to that point. The overarching mystery Ray raises is why Jayavarman IV would abandon water-rich Angkor at all: as Ray tells Gates, 'All the early capitals were there. Why? Water. They had the greatest lake in Southeast Asia.'
Mainstream archaeology holds that Koh Ker's rise and fall were closely tied to the ambitions — and political vulnerabilities — of Jayavarman IV, who is believed to have seized power outside the conventional line of succession. Ray hints at this on camera, beginning to explain the concept of primogeniture before the transcript breaks off. The absence of a clear hereditary succession system in the Khmer Empire is thought by many scholars to have made Koh Ker's status as capital inherently unstable, dependent entirely on one ruler's personal authority.
The question of the golden linga is one the episode takes seriously without overclaiming. Inscriptions at the site are understood by researchers to describe a sacred linga of extraordinary size once installed at the pyramid's summit, but no physical trace of the object has been confirmed in modern times. Whether it was removed, melted down, hidden, or simply lost to the jungle remains genuinely open. The 50-foot central shaft that Gates explores is one of the key architectural features that has drawn archaeological attention, though its precise function and whether it ever contained ritual objects is, as far as available evidence suggests, still debated.
Gates' episode contributes a vivid on-the-ground portrait of Koh Ker's isolation and scale, and Ray's expertise helps frame the site's historical stakes honestly — the episode explores rather than resolves, which is appropriate given that scholars are still working to understand why this extraordinary city was built, and why it was so quickly left behind.
According to the transcript, Nick Ray — Gates' expert contact at the summit — literally wrote the Lonely Planet guide to Cambodia, making him one of the most published non-academic authorities on the country's sites.
Koh Ker is believed to have served as the Khmer capital for only a brief window in the early 10th century, making its massive pyramid all the more striking as a monument to an empire's fleeting ambition.
Inscriptions at the site suggest the golden linga once installed at the pyramid's summit was estimated at roughly 15 feet tall — a scale that would have made it a truly monumental ritual object by any standard.
The pyramid's roughly 50-foot central shaft is one of its most enigmatic features, and its original purpose — whether ritual, structural, or something else entirely — is not definitively established by current research.
Koh Ker is generally accessible to visitors as part of Cambodia's broader Angkor Archaeological Park network, though it lies considerably farther from Siem Reap than the main Angkor temples — roughly 120 kilometers to the northeast. An entrance fee is typically required, and the journey involves travel over provincial roads, so checking current local advisories and road conditions before visiting is recommended. Climbing on Prasat Pram itself may be restricted or regulated depending on current conservation guidelines, so visitors should confirm access arrangements on arrival.
Siem Reap, Cambodia — approximately 120 kilometers to the southwest.
The dry season, roughly November through April, is generally considered the most comfortable time to visit, as the roads to Koh Ker can become difficult during the wetter months. Visiting in the cooler early-morning hours is advisable given the physical demands of the terrain.
Cambodia National Museum, Phnom Penh
The Cambodia National Museum in Phnom Penh houses artifacts from Koh Ker and the broader Khmer civilization, providing essential scholarly and cultural context for what Gates encountered at Prasat Pram.
Guatemala Snake King Archaeological Sites
Gates investigated another powerful ancient pyramid-building civilization at the Guatemala Snake King sites, making it a natural companion piece for exploring how rival capitals and contested royal succession shaped ancient empires.
Sky Caves of Nepal
Like Prasat Pram, the Sky Caves of Nepal represent a remote, physically demanding site where Gates explored a ritual structure associated with sacred objects and a vanished civilization — raising similar questions about what was hidden and why.