Indiana Jones would feel right at home ascending to this alcove in a limestone cliff above the forest, 5km from Merabu village, where travellers left their mark some 10,000 years ago. These hand stencils and animal depictions are a small sample of the thousands found throughout the karst of East Kalimantan, most of which are inaccessible to all but the most committed explorer. Arrange a guide in Merabu.