Here is one of the finest cave systems in Europe.

A single chamber of this cave system was developed for the public since 1986.

"Do you know of a modern army camp, a training base maybe, even an old cave system?"

The cave system is the 5th largest in the state of Indiana.

It has one of the largest cave systems in the world.

It has also been reported to live in underground cave systems.

This planet seems to have a considerable number of cave systems.

Tours of the open cave system run every hour and last about two hours.

It has to be coming from farther back in the cave system.

He knew, of course, that there were cave systems just under the surface.