Former mercury mine shaft at Idrija, now a heritage complex housing a museum engine room with a preserved 1906 Siemens-Schuckert winding engine and the Kley steam pump, part of the UNESCO World Heritage Site.
Jašek Frančiščke, known in German as Franzisci Schacht and renamed jašek Borba after the Second World War, is one of the oldest preserved shaft structures of the Idrija Mercury Mine, the second largest mercury mine in the world. Construction of the shaft began in 1792 on the northern outskirts of the mine working area, under a contract for mercury supply to Spain, reaching the depth of Level XI at 271.85 metres below the surface. An electric winding engine manufactured by Siemens-Schuckert, dating from 1906, was installed and began operating in 1911; it ran continuously for nearly a century without requiring replacement parts.
After 1956, ore export was redirected to Jožefov jašek and the shaft served for timber transport and miner access until the winding engine ceased operating in 2007. A modern ThyssenKrupp elevator was subsequently installed. The building was renovated in 2003 and now houses a museum engine room, the archives of the Idrija Mercury Heritage Management Centre, and the Technical Department of the Idrija Municipal Museum.
The site forms part of the UNESCO World Heritage designation awarded in 2012.
Jašek Frančiščke, initially designated Franzisci Schacht in honour of the Austrian Emperor Francis II, was constructed beginning in 1792 on the northern outskirts of the working area of the Idrija Mercury Mine. Its construction took place during a period of greatly intensified ore extraction: under the second six-year contract for mercury supply from Idrija to Spain, annual mercury output ranged from 580 to 670 tons between 1786 and 1798. The shaft reached Level XI, corresponding to a depth of 271.85 metres below the surface.
In the early twentieth century, the Austro-Hungarian administration installed a DC-powered electric winding engine at the shaft, manufactured in 1906 by the Siemens-Schuckert factory. The engine, together with its converter station, began operating in 1911. It was designed to transport ore and materials at a speed of 8 metres per second and miners at 4 metres per second, with a rated capacity of 8 tons or 6 persons per cage. The transportation process required a team of three: a winding engine operator, a bell ringer, and an attendant. Notably, the winding engine required no replacement spare parts throughout its operational life of nearly a century.
After the Second World War, the shaft was renamed jašek Borba (Battle Shaft), though local inhabitants continued to refer to the surrounding area as 'v Frančiškah'. In 1956, a cableway was constructed between Jožefov jašek and the Separation Plant at the Smelting Plant complex, redirecting all ore export to that shaft. Jašek Frančiščke remained in active use for the transport of timber and the movement of miners; at the time of the 1956 transition, approximately 280 miners were still entering the mine through this shaft each day. The winding engine continued to operate in this function until 2007.
After 2007, a modern elevator manufactured by ThyssenKrupp was installed within the shaft, connecting the surface to Level III at a depth of 122 metres. The shaft is currently the only operationally active shaft at the Idrija site, used for transporting maintenance personnel and materials to Level III and serving as the fresh air inlet for underground workings. A pipeline within the shaft pathway pumps approximately 1,800 cubic metres of mine water per day from the pumping station at Level IX to the surface.
The entrance building of the shaft was renovated in 2003. It now serves multiple functions: a workshop for mine maintenance; the archives of the Center za upravljanje z dediščino živega srebra Idrija (CUDHg Idrija); the Miner's Rescue Station; a museum engine room containing the preserved Siemens-Schuckert winding engine; and the Technical Department of the Idrija Municipal Museum, where twenty-nine items of mining machinery and equipment are exhibited. Among these is the restored Kley steam pump, manufactured in 1893 by the Škoda works in Plzeň, which pumped water from the mine from 1895 until 1948 before being dismantled in 1955. It is considered the largest preserved steam engine in Slovenia and the largest of its type in Europe.
The shaft and its surface structures form part of the UNESCO World Heritage Site designated in 2012 under the inscription 'Heritage of Mercury. Almadén and Idrija'. Prior to the 2003 renovation, many of the exhibited machines had been displayed outdoors in the courtyard of Gewerkenegg Castle since the late 1950s, where they had deteriorated through weather exposure; the decision to conserve them in an authentic mining setting within the shaft building was taken in connection with the castle renovation beginning in 1988.