Wild Lake, a karst spring with the country's shortest river

A bottomless shaft out of sight

What you see from the bank is only the mouth. The water arrives up a steep flooded shaft that divers have followed down to 164 metres, about as deep as anyone can currently dive. Around it, walls of layered limestone rise almost a hundred metres, resting on a base of impermeable flysch that forces the water to surface right here. That water comes from far away, from the Črni Vrh plateau, Vodice, the country around Godovič, the Zala valley and, in flood, even Hotedršica.

Why it’s called Wild Lake

In dry weather the water hardly moves and the lake looks like a pond. After heavy rain it changes character, pushing out so much water that a dome up to 60 centimetres high rises in the middle, with a murmur from the air it carries. Sometimes the opposite happens and, when the Idrijca rises above the spring, the lake takes water in instead of giving it out. The outflow is the Jezernica, which runs 55 metres into the Idrijca and is, according to Idrija Tourism, Slovenia’s shortest river.

Cold-loving flowers and cave creatures

The rock wall above the water is cool and shady, and plants normally found in the Alps survive on it, leftovers of Ice Age flora. The star is the Carniolan primrose, which grows only in Slovenia. More than 150 plant species have been recorded here. Down in the siphon, divers have found olms and other blind cave animals. As far back as 1838, King Frederick Augustus II of Saxony came to see these plants, guided by the botanist Henrik Freyer.

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Walking there from Idrija

My advice is to go on foot along the Rake channel trail, the channel that once powered the machinery of the Idrija Mercury Mine. It starts at the Scopoli garden, runs between oaks planted in 1776 and past the Podroteja springs, and after 2.5 kilometres reaches the Kobila dam. From there a suspension bridge takes you across the river to the lake. It’s a flat walk, with flowers from early spring.

A museum in nature

The lake was protected as a natural monument in 1967 and since 1972 it has been presented as Slovenia’s first museum in nature, with panels explaining what you’re looking at. Today it belongs to the Zgornja Idrijca Landscape Park, almost 45 km², which follows the river upstream past old timber-floating dams and gorges. No ticket office or opening hours are published. If you want more water after this, the guide to lakes in Slovenia takes you to the big ones.

If you are short on time, see the best tours in Wild Lake and pick one that fits your day.

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