Iconic watchtowers which featured in a Hollywood film and was at the centre of the real life location where 8,000 people were murdered by Nazis has been visited by an urban explorer . Located in the southern area of Krakow, Poland , the tower dates back to 1873 when its owner, Bernard Liban, opened the site to be used as a lime kiln. By 1942 the site was commandeered by the Nazis and held around 20,000 inmates, including hundreds of Roma and Polish prisoners from the Warsaw Uprising called