Geological image of the municipality reveals that most of it is constructed from carbonate aggregate. On the wide bottom of Novo mesto basin the prevailing type is shallow karst with its horizontal water pits, distinctive dinaric karst can be found on high grounds of Ajdovska plateau, Krško hills, Gorjanci and Radoha, where the prevailing type of caves is deep abyss.

In the whole municipality area over 150 karstic caves were explored and every one of them is a phenomenon in its own right. The best known cave around Novo mesto is Luknja cave. The longest of them is water cave Rupa on Brod, where it is possible to follow a 600 metres long stream; the deepest is close to 80 metres deep Straško abyss near Derganja sela. The most dismembered geomorphologic structures, calcareous sinter and abundant subterranean animal life can be found in Kotarjeva prepadna near Stranska vas and in Mihovska cave above Mihovec; Gabrska cave is famous for its location - in the centre of the village.

Tours: Karstic caves are not equipped for public visits, at times visits are possible if accompanied by experienced spelunkers.