Former gold and silver mining shaft at Banská Štiavnica, now the centrepiece of the Banské múzeum v prírode open-air mining museum, a UNESCO World Heritage Site.
Ondrej šachta is a former deep gold and silver mining shaft at Banská Štiavnica, Slovakia, dating from the late seventeenth century. The shaft reached a depth of 432 metres across fourteen working levels during its active life, which continued until its final liquidation in 1925. Following closure, the shaft and its associated štôlňa Bartolomej were selected as the basis for a major open-air mining museum, conversion of which began in 1965.
The Banské múzeum v prírode — skanzen opened to the public in 1974 and has since received more than 1.7 million visitors, offering both a surface exhibition of historic mining machinery and buildings and an underground circuit through the two uppermost levels of the original shaft workings. The site forms part of the UNESCO World Heritage property "Historic Town of Banská Štiavnica and the Technical Monuments in its Vicinity", inscribed in December 1993, and the shaft opening is listed as a národná kultúrna pamiatka (registration number 3478/1).
Ondrej šachta is located approximately one to two kilometres from the centre of Banská Štiavnica, in a valley below the Klinger water reservoir. The shaft dates from the end of the seventeenth century and was sunk into the same hydrothermal gold-silver vein systems that defined the banskoštiavnický rudný revír from its medieval beginnings. The district had been producing silver and gold since at least the eleventh century, with early open-cut extraction on the Glanzenberg ridge giving way to deep shaft mining with the arrival of German colonists from the thirteenth century.
A significant technical innovation was achieved at the Ondrej shaft in 1841–1844, when the first water-column machine with rotary motion was constructed and installed there, representing a further development of the water-powered pumping technology pioneered in the district by Matej Kornel Hell in the 1730s. The shaft was sunk progressively deeper over the following decades, eventually reaching a total depth of 432–433 metres with fourteen working levels. At its deepest extent it ranked among the deepest shafts in the district.
The Voznická dedičná štôlňa (completed 1878, 16,538 metres), the drainage and transport adit that was the principal infrastructure of the entire revír, intersected the lower levels of the Ondrej workings. The Bartolomej adit served as a secondary access and drainage work connected to the upper Ondrej levels.
The shaft was progressively wound down and was definitively liquidated in 1925. The surface complex was subsequently left as industrial ruins. In the 1960s the Slovenské banské múzeum began planning for a major open-air museum on the site. Surface conversion work started in 1965, and the Ondrej shaft itself was opened up for exhibition purposes from 1967, including a ciachovňa (assay house) and kováčska dielňa (smithy) built in the museum complex in 1976–1977. The first phase of both surface and underground exhibitions was opened to the public in 1974, and the full complex — designated Banské múzeum v prírode — has continued to develop since.
The underground exhibition follows the two uppermost working levels of the original Ondrej shaft, designated Bartolomej (approximately 33 metres below surface) and Ján (approximately 45 metres below surface), through a 1,200-metre circuit. Visitors access the underground via the ústie štôlne Bartolomej. The workings presented include hand-driven galleries from the seventeenth century as well as later blasted drifts. The surface exhibition presents an important collection of historic mining machinery transferred from other sites in the region, including a water-column hoisting machine (Kachelmannov vodnostĺpcový ťažný stroj) from the Lill shaft at Hodruša-Hámre, dating to 1881. The headframe visible over the Ondrej shaft in the museum complex is the Rúfus winding tower. The museum has welcomed over 1.7 million visitors since 1974, with peak annual attendance exceeding 52,000 in 1987.
The shaft opening is listed as a národná kultúrna pamiatka under registration number 3478/1. The entire site forms part of the UNESCO World Heritage inscription of December 1993.