The park is dominated by three mountains: Mount Mulu [], Mount Api [], and Mount Benarat []. Mount Mulu is a sandstone mountain; meanwhile, Mount Api and Mount Benarat are limestone mountains. The summit of Mount Mulu is covered by moss forests, while the limestone pinnacles are found on the upper part of the Mount Api. The Melinau Gorge separates Mount Benarat from Mount Api. Meanwhile, Mount Buda is separated from Mount Benarat by Medalem Gorge. Mount Buda is included in another national park named Gunung Buda.