The caves are located under Modoc's outhouse. A large contingent of waste has accumulated under the toilet's hole.
A lone mole rat lives in the deeper caves.
To gain access to the section with the mole rat, explosives (like dynamite) must be placed and an escape made before it explodes. After that, the Chosen One may suffer some damage and the Rose's Bed and Breakfast part of town will fill with goo.
The Modoc caves appear only in Fallout 2.
If examining a part of the goo (near the tunnel), a note will appear that there is a large amount of goo making the computer very difficult to access - a note similar to the computers in the Los Angeles Vault.[verified]