Důl Hraničná
A former iron-ore mine in the Rychlebské hory near Javorník and the Polish border, worked from the 1850s until 1968 and opened to visitors in 2019. Half of the planned underground network is flooded, and the galleries follow the magnetite ore body down at about 45°; the deepest point reached so far is 107 m below the water surface. Divers see timber supports, rails and old mining machinery in clear water. The water is 8 °C year-round at every depth and the air underground is at most 11 °C. It is one of the few places in Czechia where divers can legally dive underground, and emergency-service and police divers also train here.
depth: 0–107 m