Hill stations were a standing habit of empire across Asia - a pre-air-conditioning strategy for people who had chosen to govern a climate they could not tolerate. Bokor was Indochina's version, and it was built at speed and at enormous human cost on a mountain with no road, no water supply and no reason to be inhabited. The centrepiece, the Bokor Palace Hotel, was inaugurated in 1925: a long white block set right on the lip of the escarpment, with the Gulf of Thailand laid out below it. A Catholic church followed in 1928, still a rare thing to find in Cambodia. The Khmer royal house took to the mountain too. King Sisowath Monivong ordered a Buddhist temple built here in 1924, returned often, and died on Bokor in 1941 - which is why the national park around the ruins carries his name.

The French left in the late 1940s, driven off during the First Indochina War by insurrection in the surrounding country led by the Khmer Issarak. The mountain sat empty for over a decade. Then, in 1962, the site reopened as the Cité du Bokor, with a casino and new hotels near the lake, and for ten years it was fashionable again. In 1972 the Khmer Rouge took the area and everyone else left. When Vietnamese forces invaded in 1979, Khmer Rouge fighters dug into these buildings and held the plateau for months; the mountain remained one of their last strongholds into the early 1990s. Bullet scars and blast damage on the old walls are not weathering. Very few ruins in Southeast Asia have been fought over this recently.

Bokor makes its own weather, and it decides what you get. On a clear morning the escarpment gives you an unobstructed sweep of the coast, Kampot's salt flats, the islands and the sea beyond. On a bad afternoon the cloud comes over the edge and the visibility drops to the length of a corridor - and this, honestly, is when the place is at its best. Empty window frames appear and vanish. The church surfaces out of the mist a shade darker than the air around it. Down the road, about 10 kilometres before the station, the Black Palace, Damnak Sla Khmao, was King Sihanouk's small summer retreat; what remains of his swimming pool is a rectangle of moss. Northeast of the ruins the Popokvil Waterfalls run thin most of the year and then, after monsoon rain, do exactly what their reputation promises.

The ruins are the reason most people come, but they occupy a fraction of a very large protected area. Preah Monivong National Park was established in 1993, covers 1,544.58 square kilometres, and was named an ASEAN Heritage Park in 2003. Its forests run from dipterocarp and deciduous stands through tropical evergreen down to coastal mangrove, and they hold Asian elephants, gaurs, pileated gibbons and Asian black bears - none of which you should expect to see on a day trip. The park lost roughly 9 percent of its primary forest between 2001 and 2019. Development has arrived in force: the Sokimex Group has held a 99-year lease over the hill station site since 2008, the Thansur Bokor Highland Resort opened in 2012, a 29-metre statue of Lok Yeay Mao was inaugurated in 2012, and a 2019 government master plan proposed developing 18,987 hectares of the park.

The turn-off sits 8 kilometres from Kampot on Highway 3, or 95 kilometres from Sihanoukville; headquarters is a kilometre in, and the climb from there is 32 kilometres of smooth sealed road. Drivers who know it do the ascent in about ninety minutes. Day tours out of Kampot run cheap and take most of a day, much of it in the vehicle - and if an agent promises a sunset boat trip as part of the deal, get it in writing, because that particular misunderstanding happens with suspicious regularity. There is no entrance fee. The ranger station rents simple dorm beds for a few dollars and lets you cook if you bring food. Bring warm clothes: the days are pleasant and the nights are genuinely cold. Two things deserve respect. The summit has been cleared of landmines twice, and you should still stay on the paths. And the trails - some running two to eight hours - are unmarked and unmaintained, so hire a ranger rather than trust your sense of direction in cloud.