Only some walls of old upper Gromberg (Grüenberg) are still preserved. They can be found at the top of a steep hill above the village of Kočno above Zgornja Polskava.

This used to be a strong Roman fort surrounded by a wall and a moat. Bellow the village, there used to be another fort called Lower Gromberg (Grüenhof). Both of these castles served as the setting for Anton Ingolič“s histrical novel „Gorele so grmade“.