The Black Trout Adit (we'll get to the name in a moment!) is located in Tarnowskie Góry, just 30km north-west of Katowice. As you may know, Silesia is heavy on industrial tourism, and here you have one of 8 adits in the area. The Black Trout is special, however, as it's one of the longest underground tourist routes in Poland: found 25-30m below ground, it is 600m long, and the entire route is traversed by boat in 1hr, all while a tour guide regales you with the history and stories of the mine network it once served as a water drainage route. The name itself derives from trout that would enter from the connecting River Drama, and swimming through the water in the dim light, appeared to be black. The whole place is fantastically atmospheric, and it's no surprise it has been recognised as a UNESCO World Heritage Site. Note, there are two entry points called Ewa and Sylwester, both of which lead down through narrow shafts - maybe not the best place for those who dislike confined spaces, though ideal to visit on a hot summer's day! Note, tours are offered in the following languages: Czech, English, German, Russian and Spanish.