It took us three days to find the Marina pećina cave which was marked on an old topographic map of the Mala Rijeka canyon but dense tree cover made it impossible to find it from the ground. Finally, drone helped us locate the likely entrance which then required rigging an 80 m rope descent. The cave came out to be massive inside, with quite beautiful formations and remains of human presence. We updated the Marina pećina location on OpenStreetMap as precise as possible but we still have no idea how people were able to access it without rope, either from the top of the cliff or from the bottom of the valley.