Toxic caves

The toxic caves are north of Klamath. Before the Great War, it was a military warehouse of some sort. Now, it's a radioactive cave inhabited by geckos (little and gold, though mostly gold). Smiley, the trapper from Klamath, is waiting at the end of the second level for someone to save him.

Layout
Every step in the green sludge inflicts damage, unless rubber boots are in the Chosen One's inventory. Party members will also require boots in their inventory. Boots can be found on the first level in the caves and in Trapper Town. The boots have a chance to melt as one crosses through the sludge. At higher levels (significantly above the levels which the quest was designed for), boots may be completely unnecessary, as the Chosen One and their party will have enough resistance to shrug off the damage or take none at all. Wearing power armor will also negate the sludge's effects. If the Chosen One takes enough unprotected steps in the sludge, they may grow two extra toes a month later.

The military storehouse on the third level is only accessible much later in the game, as it requires at least 50-60 Repair skill to fix the generator for the lift, then a set of electronic lock picks to get into it (in the unpatched game, the electronic lock pick Mk II doesn't work). In its entry hall, there is a Security Bot that will attack immediately (it only uses its rocket launcher).

Appearances
The toxic caves appear only in Fallout 2 and is mentioned in the Fallout Bible.