Finally, in 1992, helped by photography from the space shuttle, they located the ruins in a collapsed limestone cavern almost underneath their base camp.

Excavating beneath an ancient fort, they found a limestone cavern into which the fort collapsed after an earthquake.

The limestone caverns were formed over time, as water seeped into and dissolved local bedrock, forming stalagmites, stalactites and flowstones.

Some of the limestone caverns are open to the public.

A 1.7 km/5577 ft length of twisting, turning limestone caverns have been outfitted with metal walkways, becoming quite narrow at some points, and subdued lighting.