The Bela Peč/Weissenfels Castle standing on a hill in the Karavanke Mountains between Kranjska Gora and Trbiž/ Tarvisio is one of the youngest medieval castles in the territory of the former Province of Carniola and one of the rare castles that were completely rebuilt by the Counts of Cilli. Around 1431 Frederick II of Cilli undertook its construction in a highaltitude and strategically important location. The castle lost its original significance already in the second half of the 16th century and began to crumble into ruin in the 17th century. Regardless of its modest remains, the building plan of the castle is still clearly discernible and reveals that its development spanned at least four building stages during the 15th and 16th centuries. In the first building stage until 1456 an extensive enclosed castle core was built, which was reinforced with an outer anti-Turkish bailey during the second and third building stages and added new tracts of buildings. The last construction works within the castle compound were performed after the earthquake of 1511, which did not significantly change the layout of the earlier building stages.