Phu Mu is a small mountain in northeastern Thailand, close to the border with Laos. A long time national forest, it has recently been turned into a national park, but most of the mountain is still outside the controlled area. During the American war, the mountain hosted a US base that was used for communications surveillance of the Vietcong across the river.
The top of the mountain offers spectacular views over the surrounding plains. It is easy to imagine how back in the 60's elephants could be seen roaming the land from up here and how US servicemen who guarded the perimeter were afraid of the tigers hidden deep in the forest. These days are long gone, and even the wild boar (ภูหมู / phu mu = pig mountain), which once were the namesake of the mountain, have become extinct. Nevertheless, the dense forest is brimming with wildlife, including monkeys, strange birds and poisonous birds. Exercise caution, you have been warned.
The mountain, like all in the region, is composed of solid sandstone. The top plateau, especially, is of interest, because in many places it breaks off suddenly, offering steep walls and broken off boulders that tumbled into the forest below a long time ago. Accessing these boulders can be difficult due to the dense, thorny undergrowth, the impenetrable bamboo and the tick cover of leaves, under which the snakes hide.
If you do venture into the jungle, however, and you are well prepared - bring a machete and proper shoes, at the very least - you will be rewarded with perfect, unclimbed boulders to last for many more years of exploration and climbing.