Mercury was discovered in Idrija (known as Idria under Austrian rule) in the late 15th century (various sources cite 1490,[6][7][8] 1492,[9][10] and 1497[6][8]).

In the Middle Ages, Idrija was managed by the Patriarchate of Aquileia and the Counts of Gorizia as part of the Governorate of Tolmin, which became independent in the 15th century.

[18]According to legend, a bucket maker working in a local spring spotted a small amount of liquid mercury over 500 years ago.

The lower levels, which extend to almost 400 meters below the surface and are no longer being actively mined, are currently being cleaned up.

The parish church in the town is dedicated to Saint Joseph the Worker and belongs to the Diocese of Koper.

There are three other churches in Idrija, dedicated to the Holy Trinity, Saint Anthony of Padua, and Our Lady of Sorrows.