The Kaarnavuori cliff rises around 45m above the surface of the lake and was formed in a spot where two fault zones intersect at angles of 110o and 20o. Kaarnavuori is a more intact part of the bedrock than its surroundings and received its castle-like shape when repeated glaciation eroded the more fragmented rocky areas down into deep valleys. One special feature of Kaarnavuori is the 6m x 10m ledge on the upper part of the cliff, the largest such ledge in Finland. The ledge was formed when the mass of rock below it collapsed due to erosion by waves and ice when the waters of ancient Saimaa were higher. One story tells that there is a door under the ledge and behind it, inside the rock giant`s home.