The Sfendoni cave is at the entrance of Zoniana, at a spot overlooking the valley of Mylopotamos. It develops within the limestone rocks of Tripoli and near phyllite-quartzite rocks.
It was created by the movements of a large fault in the area as well as the water. The cave is 3000m2 in area. It is accessible to the public and people with disabilities for an impressive 270m long route.