The Temple of Preah Vihear is a Khmer sanctuary built on the lip of the Dângrêk escarpment, the long sandstone wall that separates the Cambodian plain from the Thai plateau. The temple itself is Cambodian, dedicated to Shiva, and its builders, working over several centuries from the ninth century onward, laid it out as a long axis climbing from the plain to the cliff edge instead of the usual compact tower on a square.
That axis is what makes it special. You pass through a succession of gopuras and causeways, each higher than the last, and at the end the stone floor simply stops above a drop of several hundred metres, with Cambodia's forests spread out below. The sandstone carvings, lintels with Vishnu and the churning of the ocean among them, are worn and warm to the touch. The temple was the subject of a long dispute between Thailand and Cambodia, taken to the International Court of Justice in 1962 and again later, and the border area has had tense moments since. Check current access rules before you ride up, because crossing points and permissions have changed more than once.
The approach on the Thai side is a proper mountain road, climbing through dry dipterocarp forest in steady bends with short, steep pitches. The surface is generally good tarmac, but heavy rain loosens gravel on the corners and the mist can sit on the escarpment in the cool months. Early morning is the right time, when the air is clear and the haze has not yet blurred the plain. Traffic is light apart from weekend tour buses.
Practicalities are simple. There are food stalls and drink sellers near the car parks, and Thai highway stations are plentiful on the main routes, but not on the climb, so take fuel in Kantharalak. Bring water, a hat, and shoes with grip, since the stone steps are polished and the walk to the cliff edge is longer than it looks. Keep to marked paths, as the area has had unexploded ordnance from past conflicts, and treat any no-go sign as a hard rule.