Mulu Caves & Pinnacles, Sarawak

Gunung Mulu National Park contains four of the world's ten largest cave chambers, including the Sarawak Chamber with a floor area of 600 by 415 metres — large enough to park 40 Boeing 747s. The separate Pinnacles trail, a demanding two-day hike to 45-metre razor-edged karst formations protruding from the jungle canopy, is among the most spectacular hiking goals in Southeast Asia.