Way back when, if you wanted to brew beer in Nuremberg you need to have a cellar, both for fermentation and storage.   The cellars consist of a system of narrow tunnels and caverns that run under Nuremberg’s old town. Dating back to 14th century there were about 40 breweries in the small city all of which required a cellar of their own. This is how the extensive system of passages, some with several different levels, came to be. Today, they measure more than 20,000 m2, making them the largest labyrinth of underground passages in southern Germany.  During WWII these were used as bomb shelters, and as secure storage for all art and treasures from the castle.