Vražji Prolaz: the Devil's Passage Canyon Walkway at Zeleni vir

Vražji prolaz is a slot canyon cut by the Jasle stream into the limestone of the Gorski Kotar plateau, the high, forested belt between the coast and the Pannonian plain. The water carved a corridor roughly 800 metres long whose walls close to about two metres in the narrow sections — dark, dripping rock where the stream runs beneath the walkway and ferns hang from the seepage lines. A fenced timber walkway on frames and stairs carries visitors the full length of the slot; the fence is the reason the site works for families, and the helmet rule is the reason it works at all, since small rockfall from the canyon walls is a standing hazard.

The canyon is only one piece of a reserved landscape: in 1962 the area was proclaimed a special geomorphological reserve covering 200 hectares, and the Zeleni vir excursion site at its heart has been a Gorski Kotar outing since the 1920s, when the little Munjara hydroelectric plant was built at the spring in 1921 — it still turns on its original machinery, and in its day it supplied the whole region with electricity.

The loop begins at the excursion site by the Zeleni vir spring, a pool of opaque emerald water resting in the bottom of a shallow cave at the foot of a rock face about 70 metres high. Two streams pour from the top of that wall; one falls as a free waterfall in front of the cave mouth — the fall local and tourist-board sources call Skakavac — so you watch it through a curtain of water, and the cave behind the fall holds its own green lake. Below, the water turns the 1921 Munjara turbine.

From the spring the trail climbs into the canyon itself. The fenced walkway crosses and re-crosses the Jasle on footbridges, squeezes through the two-metre narrows and climbs dry-slate stairs for the full 800 metres; the air inside is canyon-cold even in August, which is precisely why Fužine and the coast use the site as a cool-air escape at the peak of summer. At the canyon's end the route rises 14 metres above the stream to the entrance of Muževa hiša, a cave about 200 metres long that ends in a chamber with a small lake — strictly protected horseshoe bats roost inside, so the rule is quiet passage and no lights on the roosts. The return leg follows the geological and botanical educational trails back to the site.

• Zeleni vir spring: emerald pool in a shallow cave below the 70 m wall.
• The waterfall in front of the cave mouth — photographed through the falling water.
• The fenced canyon: 800 m on walkways and stairs, helmets obligatory.
• Muževa hiša cave: ~200 m, a lake at its end, protected horseshoe bats.
• Munjara, the 1921 hydro plant still running its original machines.

The circuit stop by stop

Timings below assume a family pace with photo stops; fast walkers do the loop in half the time.