What are Exo Terra Big Rock Caves. The Exo Terra Big Rock Caves are the new eco-friendly range of caves from Exo Terra. They come in 2 sizes; small (11cm x 13cm x 8cm), and medium (15cm x 18cm x 11cm). Key features: good hiding spot for reptiles Ideal for Leopard geckos Contains a water reservoir good humid microclimate which is good for egg laying Integrates into any type of terrarium due to its natural look What are the features of these caves. The caves contain a water reservoir which slowly releases moisture into the cave and due to the hygroscopic properties of the ceramic material it helps regulate the cave's humidity and temperature. The Exo Terra Big Rock Caves are good for species such as leopard geckos which require a vivarium that has a hot and a cool side. Due to the water reservoir on top placing the caves on separate ends will change the humidity of the vivarium. Without having a hiding place, a lot of reptiles can become stressed, which will affect their health, appetite and activity.