The ruins of the small fortress called Údolský Hrádek are situated on the small rock pit above the pond in Josafatské Údolí (Josafat Valley) about 7 km east of the small town Chýnov.

The fortress was founded in the first half of the 14th century probably by the Lords of Hradec. It was destroyed on the unknown circumstances as early as at the end of the first half of the 15th century. In the modern period the mill was built next to the fortress and most of the building material for the mill was used from the ruins. The mill is in ruins in present.

The ruins are accessible along the yellow tourist sign from the settlements Nové Dvory (about 1 km) or Sudkův Důl (about 2.5 km).