Whether you are a cave explorer or a curious traveler, Gomantong Caves is one of the many highlights of Sandakan which you must visit at least once in your lifetime. However, if you are at all squeamish about creepy-crawlies of any sort, you might want to think twice about going there.

Located within Gomantong Hill, the hill is the largest limestone outcrop in the Lower Kinabatangan area. The cave system is made up of two primary chambers, the more accessible Simud Hitam (Black Cave), and the larger Simud Putih (White Cave). The names refer to the main type of nests produced by swiftlets in each cave.

Gomantong Caves - Wikipedia

Simud Hitam’s ceiling can reach 40–60 m (130–200 ft) high. It is the source of the less-valuable “black saliva” nests. These contain both feathers and saliva and require cleaning afterward. Whereas Simud Putih is not open to the general public, and access requires appropriate caving equipment and experience. It is where the more valuable “white saliva” nests of the swiftlets are found, and is reached by a steep, 30-minute climb further up the mountains. The main entrance is located above and adjacent to the main “lighthole” at the back of Simud Hitam.