It was here in 1490 that a rich deposit of mercury ore was discovered. Now, Idrija's famous mercury mine, which was the second largest mercury mine in the world, has closed after 500 years. In spite of this, the people of Idrija are committed to preserving the miners' tradition and cultural heritage. The oldest part of the mine - Anthony's Shaft, which dates from the year 1500, and the underground chapel from the 18th century - is open for visitors. The magnificent Gewerkenegg Castle from 1533 houses the extensive collections of the Idrija Municipal Museum, which was declared the European technical and industrial heritage museum of 1997. The castle courtyard also serves as a venue for summer cultural events.