An underground den and a balanced diet are crucial to the health of captive tortoises.

After 1917, when Storyville was shut down, separate black and white underground dens of prostitution emerged around the city.

Its underground dens are up to 5 feet (1.5 m) long.

This underground den was located beneath an old garage.

Ten more were stationed outside, covering the entrances to this underground den.

One of the encyclopedias had a drawing of their underground den.

Behind him showed a dim stone stairway which he had used to reach this underground den.

Up to eight skunks may share an underground den in the winter.

They flee the forge through more dark tunnels and escape to Guthwulf's underground den.

In a way, it was as if they still lay twined together like animals in an underground den.