Cross Cave, Show cave and archaeological site in Cerknica, Slovenia.

Cross Cave (Križna jama) lies in the Lož Valley between the Lož Karst Field, Cerknica Karst Field and Bloke Plateau. At Calvary it splits into two branches: the Muds to the north and the Variegated Passage to the northeast, which is reached by small boats and passes the Matjaž Passage with its large columns before the Crystal Mountain, the largest room, where visitors climb a pile of collapsed rock above the stream.

Cross Cave was first documented in 1832, while its lake and stream passages were explored by Slovene cavers only after 1926. The cave was prepared for visits in the 1950s by the Lož Valley Tourist Association, later managed by the Ljubljana Cave Research Society, and since the 1990s cared for by the Friends of Cross Cave Association. Over two thousand cave bear bones have been found here, and ceramic and lithic remains from the Eneolithic period were discovered near the entrance before the first lake.

The cave takes its name from the Holy Cross Church in Podlož. Since the 1990s the Friends of Cross Cave Association (Društvo ljubiteljev Križne jame) has cared for it, after the Lož Valley Tourist Association prepared it for visits in the 1950s and the Ljubljana Cave Research Society managed it later. Boats are used on the Variegated Passage, and the Matjaž Passage holds large columns called King Matjaž's pillars.

The flooded section is limited to four visitors per day, so book ahead. The Variegated Passage is reached only by small boat, and the water stays around 8 °C. The cave lies in the Lož Valley between the Lož and Cerknica karst fields and the Bloke Plateau.

The cave system is home to roughly 45 different animal species surviving in low-nutrient conditions. This biodiversity makes it one of the world's most biodiverse underground environments.