The Merkenstein ruins are the remains of a castle in Lower Austria near Bad Vöslau in the Großau cadastre (property register).

[1] In the 1600s, Merkenstein controlled Gainfarn, Großau (in Bad Vöslau), Pottenstein, Furth, Muggendorf and St. Veit (in Berndorf).

Until the end of World War II, the castle and its precinct belonged to the Krupp family.

In October 2008, the Austrian TV crime drama Vier Frauen und ein Todesfall (Four Women and a Funeral) was filmed at the ruin.

The top layer of sediment showed that the cave was a place of refuge during the Turkish wars of 1529 and 1683.