Terezín is one of around 50 fortified ideal towns in Europe. Terezín, named after Empress Maria Theresa, was built by the Habsburgs against Prussia in 1780-90 in the area where the Eger flows into the Elbe. The imposing, ideal fortress city with an underground mine system around 20 kilometres long is one of the largest fortresses in Europe. Terezín became sadly famous during the Second World War as a Nazi ghetto and prison. Today, the Small Fortress is a reminder of the dark past, while the fortress town represents the fortress with its military history.