Idrija mercury mine

Two mines on different continents share one World Heritage listing, because between them they supplied the world with mercury.

Idrija is a town in western Slovenia, seat of its own municipality, lying in the Idrija Basin among the Idrija Hills and traversed by the Idrijca River. Mercury was found here in the late 15th century; sources put it at 1490, 1492 or 1497, and UNESCO uses 1490. That discovery made the town, and the town has been shaped by it ever since.

The listing it shares is called Heritage of Mercury, and it pairs Idrija with Almaden in Spain, where mercury has been extracted since antiquity. Together they are the two largest mercury mines in the world, both working until recent times. What UNESCO singles out at Idrija is not a single monument but the whole apparatus of a mining life: the mercury stores and infrastructure, the miners' living quarters, and a miners' theatre. The sites are listed for bearing witness to the intercontinental mercury trade, which drove exchange between Europe and the Americas across centuries, because mercury was what made New World silver refining possible.

The town's history runs alongside the mine. In the Middle Ages Idrija was managed by the Patriarchate of Aquileia and the Counts of Gorizia as part of the Governorate of Tolmin. After 1500 it was held for a year by the Republic of Venice, in 1508, but otherwise governed by the Habsburgs. The 1511 Idrija earthquake struck in March of that year. To support the mining, the mine owners built Gewerkenegg Castle between 1522 and 1533, and operations were later taken over by the government.

There is more here than the mine. Idrija lace is a bobbin tape lace with its own protected geographical indication from the Slovenian Intellectual Property Office, and in 2011 the town was named Alpine Town of the Year. Mercury is toxic and this is a heritage site rather than a collecting ground, so come to see how it was done, not to take anything home.