The Deraniyagala Cave is one of the most famous sights found in the sprawling Boulder Gardens built among the rocks which lie at the feet of the imposing Sigiriya rock. The cave itself, which is actually more of an overhanging rock ledge, was a shelter once used by monks and actually pre-dates the Sigiriya fortress.
The cave's main claim to fame are the faint and now barely-visible paintings of aspara (a sort of heavenly nymph reminiscent of the famous Sigiriya frescoes found in a cave on the rock itself) which were created around the 2nd century BC. Like I said, the paintings are very faded and at first glance you won't notice them. Take some time to really examine the cave walls and you'll suddenly begin to notice arms, breasts, and feet in what you first thought were just natural stains on the rock.