For centuries, Idrija was a centre for the mining of cinnabar, the raw material for mercury. The cinnabar deposits discovered in 1490 were exploited by the government of the Habsburg Empire from 1509 onwards and smelting works were built on the banks of the Idriza to the north-east of the town centre. Over the centuries, several shafts were sunk, making Idrija one of the largest mercury mines in the world. At the end of the 18th century, no fewer than 1,350 miners worked here. The Idrija mercury mine, together with the Almadèn mine in Spain, was inscribed on the UNESCO World Heritage List in 2012.
The history of mining is presented in detail in the Idrija Municipal Museum in Gewerkenegg Castle, including in the exhibition area "Five centuries of cinnabar mining". The castle was built in the 16th century as a mine administration building and storehouse for the extracted mercury; it has been used as a town museum since 1954.
Restored mining machinery and equipment such as pumps, a turbine, locomotives and machine tools from the maintenance workshops are on display at Francis' shaft, a branch of the town museum. The shaft itself was built in 1792 and is still in use today with its surface buildings preserved, including the headframe for underground inspection work. Just 50 metres away, the museum displays an 18th-century miner's house. In Kamšt, you can see a water-driven mine pump with what is probably the largest wooden driving wheel in Europe, measuring 13,6 metres in diameter.
An underground visit is possible to the Anthony's shaft, which was sunk in 1500 and is one of the oldest preserved mine shafts in Europe. The underground tour leads 1,200 metres into the mine's tunnels. Audio-visual presentations and figurative displays explain the mining methods used.
In the Hg Smelting Plant, VR glasses allow visitors to virtually experience the process of extracting mercury by heating cinnabar in a rotary kiln.