The Poneryotka is a river which partially runs beneath the ground and flows into the Msta near the Borovichi rapids. It starts from Lake Shitikovo at an altitude of 159 metres.
The Poneryotka forms one of the largest cave systems in the central part of the Russian craton, including underground chambers, tunnels, lakes, water holes, pathways, syphons, cliffs, and galleries dozens of metres long where people can walk without bending over.
