The ruins of the Janštejn castle (also called "John's Castle" or "John's Stone") are located about 6 km south of the village Horní Cerekev and about 2 km east of the small village Horní Dubenky.

The castle was built probably around 1315, when the domain of the small town Počátky was founded. In 1358 Štepán from Březnice sold the castle with Počátky to the Moravian margrave Jan. Janštejn was damaged probably during the Hussite wars, when several villages and settlements in the surroundings were destroyed.
Only small remains of the tower and bulwarks have been preserved up till present.

The castle is accessible along the yellow signed tourist path, turning-off to the left from the road Horní Dubenky - Batelov, about 2 km behind Horní Dubenky. The ruins can be found about 150 m far from this road.

The small memorial to the battle on the 7th december 1423 can be found by the forest pond, about 500 m south of Horní Dubenky. That day the batalion of Menhard from Hradec conquered the batalion of Tábor soldiery led by Jan Hvězda from Vícemilice. The pond has been called "Bloody" since that time because the water in the pond was supposedly coloured red by blood of killed fighters after the battle. The parts of weapons, clothing etc. from the battle can be found there in present.