Arneševa luknja is the most famous cave in the Udin boršt forest in the Gorenjska region - a place that has fascinated travelers and researchers for centuries. It was already mentioned by Valvasor in his 1689 work, where he named it Felsen-Grotte bei Duplach. It is the largest and best-known cave in this remarkable conglomerate karst area.

A spring flows from the cave, and locals have used it as a source of drinking water for generations. Inside lies a spacious chamber, and during dry periods it is possible to penetrate horizontally as deep as 800 meters. The surrounding forest, dominated by red pine along with sessile oak, hornbeam and beech, creates a calm, shaded atmosphere that is especially pleasant in spring and autumn.

The wider Udin boršt area is one of the oldest glacial terraces in the Ljubljana Basin, and the conglomerate near Arneševa luknja has been dated to 1.86 million years old.

• Spodnje Duplje or Zgornje Duplje - easy forest path, walking time depends on starting point, easy difficulty
• Accessible also via the Kranj-Golnik road or the old Kranj-Tržič road

• The cave lies within the Udin boršt Landscape Park, where nature protection rules apply
• Introducing non-native plants and animals is forbidden, as is making noise above 45 dB
• Deep exploration is only possible during dry periods

The spring emerging from Arneševa luknja has supplied drinking water to nearby villages for generations, making this cave not just a geological curiosity but a cultural landmark of the region.