The Klavže at Idrijska Bela are a surprising piece of engineering, a huge stone wall built across a narrow gorge in the eighteenth century, with a gate in the middle. The idea was brilliant and simple. The mercury mine at Idrija, one of the largest in Europe, needed vast quantities of timber for its shafts and furnaces, and the forests were in the hills, far from the town. So the woodcutters piled logs behind the barrier, the gate was opened and the stored water carried the logs in a rush down the stream to the mine. Such water barriers, called klavže in Slovenian, were used here for generations, and the one named after Putrih is among the grandest.
The barrier belongs to the heritage of the Idrija mercury mine, which UNESCO listed in 2012, along with the Spanish mine of Almadén. The town itself is a charming place, and has a distinctive tradition of bobbin lace, taught in the local school, and a dish of small dumplings called žlikrofi, filled with potato and herbs and served with meat sauce. The mine was a source of wealth for the Habsburg monarchy, and it carried a high human cost, since mercury poisoning was a constant risk for the miners.
The setting is dramatic: a deep, narrow valley with beech and fir forest, the clear water of the Belca stream and a path that leads along the water to the stone walls. The place is quiet and cool, and in spring the stream runs high. The walk is short and well kept, and the huge wall rising from the gorge is an impressive sight, even more so when you think of the labour that built it.
Riding here is a delight. The roads around Idrija climb and fall through forest, with curves that are tight enough to be fun and a surface that is generally good. The route from Ljubljana via Logatec is a classic, and the way on toward Cerkno and the Soča valley is just as good. Traffic is usually light, but forestry trucks use the narrow roads. Early autumn, with colour in the beeches and fewer visitors, is a splendid time. Winter can bring ice in the shaded gorges, so take care.
Idrija, about eight kilometres away, is the place for fuel, food and a bed, and the cafe tables in the main square are a good place to enjoy a cup of coffee and a slice of local cake. There is little in the small villages along the way.