Slovak opal mines – Gateway tunnel JOZEF

The opal mine has 17 levels, 4 of which are flooded, and the deepest point is almost 70 m below the water level. The flooded tunnels stretch for almost 5 km. The water temperature is 4-5 ° C, visibility is about 20 meters, but it deteriorates quickly due to soft sediments on the walls and ceiling.

There is no life to see underwater due to the very low ph-level of the water and the lack of reaching daylight.