Built in the early 12th century by the Khmer king Suryavarman II in present-day Cambodia, Angkor Wat originally covered 162.6 hectares and, unlike most Khmer temples, faces west. Scholars debate whether that points to a royal mausoleum, since its bas-reliefs lead visitors counterclockwise as in funeral rites, or to its dedication to Vishnu. Its five towers represent the peaks of Mount Meru, its moat the cosmic ocean, and at the spring equinox the sun rises over the central tower. A 35 kilometer canal carried sandstone from Mount Kulen, and a 2015 University of Sydney LiDAR survey revealed roads, houses, and ponds for up to 4,300 residents inside the walls.

After the Cham sacked the empire in 1178, Jayavarman VII and his wife Indradevi steered it toward Buddhism, and the temple became a Theravada site that monks maintained for centuries. Japanese pilgrims visited, and Ukondayu Kazufusa celebrated Khmer New Year there in 1632, long before Henri Mouhot was guided to the site in 1860 and wrote of a lost civilization, a story France used to justify its 1863 protectorate. The temple later took bullets during fighting between the Khmer Rouge and Vietnamese forces, lost statues to armed looters, and was damaged by cement repairs before leaving UNESCO’s endangered list in 2004.

• The Churning of the Sea of Milk relief, with 92 asuras and 88 devas possibly marking the days from solstice to equinox
• Nearly 1,800 devata carvings showing real 12th century Khmer hairstyles, garments, and jewelry
• How LiDAR filters out tree canopy to expose a hidden grid city beneath the forest
• Why impermeable cement and harsh chemicals trapped moisture and fed microbial biofilms in the sandstone
• Visitor numbers rising from about 7,654 in 1993 to 2.6 million in 2018, and hotel water pumping that threatens the sandy foundation