Lipnica Castle stands on a limestone bluff about 2 km south of Radovljica, above the confluence of the Sava Dolinka and Sava Bohinjka rivers. The ruins date from the 12th century and the castle changed hands repeatedly through the medieval period. It was largely destroyed in the 17th century and has been a ruin ever since, though the remaining walls are still substantial enough to give a sense of the original fortification.
The walk up from the road takes about twenty minutes through mixed forest. At the top, the views across the Sava valley and toward the Karavanke range are worth the effort even if you have no particular interest in ruins. The site is not formally managed — no entrance fee, no facilities — so it is best visited on a clear day when you can make the most of the panorama.