Gomantong Caves, Limestone cave system in Kinabatangan, Malaysia.

Gomantong is a limestone cave system in the Kinabatangan region featuring two main chambers called Simud Hitam and Simud Putih that run through a massive limestone outcrop. The caverns contain thick guano deposits and shelter numerous bird species alongside millions of bats.

Initial investigations of guano deposits began in 1889 when the China Borneo Company explored the site for commercial use. The first systematic cave mapping took place in 1930, revealing its full structure to the outside world.

Local harvesters enter the caves seasonally to collect valuable edible bird nests using traditional climbing techniques with bamboo and rattan equipment that has remained largely unchanged for generations.

Wear sturdy shoes with good grip since the paths inside are slippery and uneven, especially where guano covers the floor. Expect humid and warm conditions, and allow your eyes time to adjust to the dim light inside.

The bat colony was counted at 275,000 to 276,000 wrinkle-lipped free-tailed bats in 2012, after earlier figures had been widely exaggerated. Bat hawks wait near the cave mouth and hunt the bats as they leave the roost at dusk.