UNESCO's World Heritage Committee has decided to include the Idrija and Almaden mines on its heritage list at its session in Saint Petersburg on 30 June, after the two countries submitted a joint bid, which focused on the technical heritage connected to the two of the world's biggest and most representative mercury mines.

Slovenia's bid was conceived in 2006, initially as a part of the intercontinental mercury and silver route "Camino Real" (Royal Path), which also included Peru's Huancavelica.

Later, the bid was slightly changed to feature Almaden and the San Louis Potosi silver mine in Mexico. But the trio did not get sufficient support at the committee's sessions in Seville and Brasilia.

After Mexico abandoned the project, a new bid was forwarded to the UNESCO World Heritage Centre in February 2011. This time the focus was on mercury - the technological and industrial procedures that helped shape cultures, economies and brought about social changes.

Idrija's mercury mine is one of the biggest decommissioned mercury mines in the world, since about 13% of all the mercury ever produced worldwide came from Idrija, where mining was the main industry for five centuries.

The production of mercury ended in 1994. When the closure was launched in 1977, the main reasons were low prices of mercury and partial depletion, while later environmental concerns prevailed.