Francisca's Shaft 20% off entrance fee to Francisca's Shaft in the Idrija Mercury Mine. A guide from the City Museum of Idrija is needed. In an authentic mine environment – the building of Francis' Shaft, 29 machines and devices representing precious specimens of the mine's technical heritage are on display. The restored Kley's pump is the largest preserved machine of the Idrija Mercury Mine, as well as the largest preserved steam machine in Slovenia and probably also in Europe.