The vestiges of the Celtic primeval fort Obří Hrad (Giants' Castle) have been preserved above the valley of the Losenice river near the settlement Popelná (about 6 km south-east of the small town Kašperské Hory) in the National Park Šumava (Bohemian Forest), 1,005 m a.s.l.
It is considered to be the most important iconic Celtic place in the contemporary territory of the Czech Republic.

The remains of the Celtic fort can be found on the red marked trail about 7 km away from the small town Kašperské Hory. Access is possible from the small village Nicov along the blue and yellow marked trails to Popelná and then continuing along the red marked path or also from the top of Churáňov mountain (the red sign joins the blue one - about 10 km). The seas of stones can be seen on the way along the Losenice river.
The instructional trail Keltové na Šumavě (Celts in Šumava) leads from Popelná to the fort.

The area is a part of Zone I of the National Park Šumava.