Koh Ker is a remote archaeological site in the jungles of northern Cambodia, located roughly 120 kilometres (75 mi) from Siem Reap and the temples of Angkor. Within a protected area of 81 square kilometres (31 sq mi), more than 180 sanctuaries have been identified, though only about two dozen are currently accessible to visitors — the rest remain hidden in dense forest, and much of the surrounding area is not yet fully demined. The site's most dramatic feature is a 36-metre (118 ft) seven-tiered pyramid, believed to have served as the state temple of the Khmer king Jayavarman IV, and described by Gates as "the tallest pyramid in the entire country." Once known in inscriptions as Lingapura ("city of lingams") or Chok Gargyar, Koh Ker served as the capital of the Khmer Empire from approximately 928 to 944 AD before being mysteriously abandoned and swallowed by jungle. Gates traveled here to investigate why this ambitious city was built in such a remote location — and why it collapsed so suddenly — joining an international team of archaeologists working to recover looted and buried sculptures.
Jayavarman IV moves the Khmer capital from Angkor to Koh Ker, initiating an ambitious building program that includes dozens of temples, reservoirs, and the seven-tiered pyramid.
Under Harshavarman II, Koh Ker is mysteriously abandoned and the capital returns to Angkor. The city's ruins are gradually reclaimed by jungle.
Koh Ker is inscribed on the UNESCO World Heritage List on 17 September 2023, during the 45th session of the World Heritage Committee in Riyadh, Saudi Arabia.
Gates investigates Koh Ker in Expedition Unknown Season 12, Episodes 7 and 8, joining excavations and exploring the site's enduring mysteries.
Mainstream archaeology holds that Koh Ker represents one of the most extraordinary — and puzzling — episodes in Khmer history. Under Jayavarman IV, who came to power around 928 AD, the capital of one of Southeast Asia's most powerful empires was uprooted from the established religious and administrative center of Angkor and moved roughly 80 miles away into remote jungle. During his reign, Jayavarman IV oversaw the construction of an enormous water reservoir, approximately forty temples, and the unparalleled seven-tiered pyramid — a design that breaks from the concentric plan typical of Khmer royal temples and follows a linear layout instead. Scholars regard the sculpture produced during this period as some of the finest in Khmer history.
The reasons Jayavarman IV chose this remote site, and why the capital was abandoned so abruptly after only about 16 years under his son Harshavarman II, remain genuinely debated within the field. No single explanation has gained universal acceptance. The site's very remoteness — far from the agricultural and hydraulic infrastructure that sustained Angkor — may have made it ultimately untenable as an imperial capital, but the political, religious, and practical factors behind both the founding and the abandonment are still being worked out through ongoing excavation and inscription studies.
On camera, Cambodian archaeologist Phin Phakdey leads Gates through the excavation at Prasat Krachap, one of Koh Ker's more substantial temples. The recovery of carved pediment fragments buried for approximately a thousand years gives a sense of what these monuments looked like at their peak — details that surface-level ruins, worn by centuries of rain and jungle encroachment, can no longer provide. The presence of Hindu iconography, including a figure identified as a Hindu god holding a lasso, underscores the religious character of Jayavarman IV's building program.
The episode also draws attention to a serious and ongoing problem: Koh Ker's remoteness made it especially vulnerable to looting, and sculptures from the site have ended up in museums, private collections, and auction houses around the world. These pieces are now considered stolen art. The inscription of Koh Ker on the UNESCO World Heritage List in September 2023 represents a significant step toward the site's protection and recognition, though Gates' episodes make clear that the work of understanding — and recovering — Koh Ker is far from complete.
Koh Ker was known in ancient inscriptions as Lingapura — meaning 'city of lingams' — a reference to the Hindu phallic symbols that featured prominently in its shrines, some reaching two meters (6 ft 7 in) in height.
The site contains more than 180 sanctuaries within a protected area of 81 square kilometres (31 sq mi), but only about two dozen are currently visitable because the rest are hidden in forest or in areas that are not yet fully demined.
Koh Ker's seven-tiered pyramid stands 36 metres (118 ft) tall and is considered the tallest pyramid in Cambodia; unlike most Khmer temples, it follows a linear rather than concentric architectural plan.
Koh Ker served as the capital of the Khmer Empire for only about 16 years (c. 928–944 AD), making it one of the shortest-lived imperial capitals of a civilization that otherwise endured for roughly 800 years.
Koh Ker is generally accessible to visitors, located approximately two and a half hours from Siem Reap by road. Around two dozen monuments are open to the public, though most of the site's more than 180 sanctuaries remain off-limits due to ongoing demining efforts and dense jungle cover. Visitors can find basic accommodation in the nearby village of Seyiong or at community-run guesthouses in the area; check current local advisories before visiting.
Siem Reap, approximately 120 kilometres (75 mi) to the southwest.
The dry season from November through April is generally considered the most comfortable time to visit, with lower humidity and more manageable jungle conditions. The wet season brings lush scenery but can make some areas harder to navigate.
UNESCO World Heritage Site (inscribed 17 September 2023)
Cambodia National Museum, Phnom Penh
The Cambodia National Museum in Phnom Penh holds significant Khmer artifacts, and the fate of looted Koh Ker sculptures — recovered or still sought — connects directly to questions of cultural repatriation that the museum is central to.
Guatemala Snake King Archaeological Sites
Like Koh Ker, the Guatemala Snake King sites represent a Gates investigation into a powerful ancient civilization whose jungle-swallowed ruins are still being decoded by archaeologists using modern technology.
Sky Caves of Nepal
The Sky Caves of Nepal, like Koh Ker, represent a remote site where Gates joins researchers working to understand a mysterious ancient culture whose artifacts have been endangered by looting and difficult access.
Historical data sourced from Wikipedia