Crossing Europe's largest underground lake was amazing. The former gypsum mine is filled with a 6,500 square metre vast lake. The tour takes you through the old mine. During World War II the Deutsche Wehrmacht used it as a secret aircraft factory. They had to pump dry the whole lake! There are still a few original aircraft objects and rusty helmets down there.
The boat tour itself takes around 15 minutes and is worth every second. My son loved the pirate ship that anchors there - it was used during the filming of Disney's The Three Musqueteers.