The Kelabit Highlands of Sarawak, Malaysia and the Kerayan Highlands of Kalimantan, Indonesia areculturally contiguous areas separated by the Apad Wat mountain range, consisting of a number ofvillages that are related ethnically, linguistically, and through marriage. Though now separated by apolitical boundary, locals have always traversed this border. Now, foreign tourists also walk across thisborder, as community-based transboundary ecotourism is often centered around long-distance trekkingamong villages. The main attractions along the way for most tourists are impressive megaliths thatinclude erected stones, carved stones, and large piles of stones, and other cultural sites such as oldlonghouse sites, and earthworks in various shapes such as crocodiles. These cultural sites, and thelandscape in which they are found, represent a complex history of movement in the landscape by various,but related, ethnic groups that predates political separation. These sites have deep cultural and religioussignificance to local people on both sides of the border, and the experience of trekking among them hassignificance beyond mere tourism for many visitors as well. There is strong local, governmental, andinternational support for ecotourism development here, as well as an awareness of the possible pitfallsof expanding ecotourism in this region. This paper provides background on elements of the landscapeitself, particularly megalithic structures located within intact rain forest, that attract visitors. It alsopresents a synopsis of some of the cross-boundary efforts to simultaneously promote responsible andculturally sensitive ecotourism development and to protect the ecological and cultural integrity of thisunique megalithic landscape in the “heart of Borneo.” Research for this article was conducted primarilyin the Kelabit Highlands, and emphasis on this area is reflected in the data and discussion.