Gewerkenegg - mine castle (in a literal translation community hill or community castle) was built between 1522 and 1533. But even before its construction a castle of patriarch of Aquileia has been witnessed on the area of Idrija - castrum nostrum de Idria but nothing is known about it. It was probably located on the area of Lower Idrija where also parish office was located. Gewerkenegg certainly is not legal successor of mentioned patriarch'a castle. It was built on initiative by Ahacij's company of mining enterpreneurs with intention to secure stocks of mercury and cinnabar (also cereals) from Venetian and Turkish intrusions. So Gewerkenegg is not a castle in the true sense of the word because it was not built as a fortified center of a dominion but as fortified main office of mining administration and a storehouse for ore.
Disagreements between partners in a mine and speculations of a court brought to nationalization of a mine in Idrija in 1575. Archduke Karel bought off shares of a mine with the castle and all other mine assets from all owners of the time which were mostly from the ranks of most noble families in Kranj like Auerspergs, Lambergs, Ekghs and Ravbars. After nationalization in 1575 the castle became residence of mine managers. In 1607 area of Idrija was excluded from Tolmin dominion. After established cameral Idrija's land dominion mine managers have also taken over a function of land lords and were until 1848 collecting land register's duties from approximately 300 subjects in Idrija area. In 1783 Idrija was also formally excluded from Gorizia region and annexed to Carniola region.
Idrija's mine and castle were Austrian national property until the end of World War I. when according to St. Germain peace treaty Idrija belonged to Italy.
Until 19^th century mercury and cinnabar were still stored in castle cellars and also cereals and other life necessities for miners until construction of a new storehouse in 1763 near parish church of St.Barbara. In 1940 mining administration moved out of the castle and 2 years later the castle was occupied by Italian army command for Idrija. Between 6^th and 14^th March 1945 the castle was pretty damaged during the British bombardment. Building was reconstructed and was until 1949 used for the needs of the court-of-law. In 1953 Idrija Municipal Museum, established in 1949, began to manage a great part of castle. Part of a castle was used by music school. Between 1988 and 2008 the building was thoroughly rehabilitated and completely rearranged for museum and other cultural needs.

Mining corporationg maintained 30 armed miners, called lancers, in the castle. Even in the 19^th century a collection of spears and uniforms of lancers and musketeers of mine militia from the era of French wars was stored in the castle.