I went a few hours East, parallel to the border to Cambodia to visit Preah Vihear. Technically, this should be under "Cambodia" where it is located.

The access is currently easier from Thailand, though, although this effecitvely requires two entrance fees and a fee for a non-visa to allow visa-less entry into Cambodia. Sovereignty over the temple was in fact the issue of a case before the International Court of Justice, which was decided on June 15, 1962, in favor of Cambodia (and against Thailand). Travel guides to Thailand are apparently all written by failed lawyers, because they invariably point out that no comment on this temple is required because it is in another country.

Architecturally, Preah Vihear belongs mostly into the same period as the other great temples North of the Dangrek range, i.e., the early 11th period (Suryavarman I) when the Khmer empire solidly expanded its influence in this area and the early 12th century (Suryavarman II, who commissioned Angkor Wat). This must have been a place of worship much longer; oldest architectural bits are assigned to the 9th century, when the Khmer empire was just taking shape and so on.

That cannot have been a start from scratch as a religious place, either, though. The temple lies on a precipice over the plains of Cambodia, with an almost birds-eye view hundreds of meters down. Supposedly, Angkor Wat is visible on a clear day, but the one I hit was the opposite from clear, and in any case I don't know what a clear day is in the tropics and how you can see for more than 150 km. Anyway: here goes...