Castle Gewerkenegg is located on a small hill in the old town centre of Idrija. The renaissance castle was built in the 16th century for the mine management and the storage of mercury. Castle Gewerkenegg was also a centre of trade with mercury in Idrija. The castle was through the centuries rearranged and upgraded. Courtyard facades were painted in the other half of the 18th century with frescoes, which are now restored and reconstructed. Today is in the castle seat of the Municipal Museum Idrija, which was proclaimed for the best European museum of engineering and industrial heritage in the year 1997. The museum was established in the year 1953. In its care are cultural, historical monuments, technical monuments, natural remarkablenesses and preserved buildings from the Second World War. In the museum they have the permanent exhibition named Five centuries of the mercury mine and the town of Idrija. Photographs of Idrija, exhibited documents, maps and original objects illustrate mining history, the development of floating timber and forestry. In the geological collection are presented minerals, mercury ores, rocks and fossils. In the castle are held many cultural events in the summer time, which attract many domestic and foreign visitors.