This beautiful, narrow gorge is over 2 kilometres in length. At its deepest it is as much as 20 metres with sides only shoulder width apart. It was formed approximately 10-15,000 years ago when enormous quantities of water from the Mostnica River, also carrying various materials, carved the rocks as it powered its way through. Four bridges and two footbridges cross the Mostnica between Stara Fužina and Mostnica Waterfall. A walk will take a few hours or guided tours can also be arranged for those wishing to learn more about the surrounding flora and fauna.