Základna Salamandry (not to be confused with the three úkryty) is a large underground complex on two levels that Geralt finds himself and an ally, either Yaevinn nebo Sigfried, teleported to by Triss Ranuncul at the end of Kapitola III. It is a series of caves connected by winding corridors. There are some less than structurally sound looking areas that require wooden trusses to support to tons of rock threatening to come crashing down.
It's the home of a kikimora colony, complete with their královna. The Salamandra took it over after figuring out a way to control the insectoids. There is also kruh živlů, the Kruh pohaslé magie tucked away not too far from Alvarův portál on the first level of the complex.