The 13th-century City Castle Oudaen has had countless residents over the centuries including knights, students and noble families. Despite their different backgrounds, they all shared a common passion: beer. In medieval times everyone, young as well as old, drank beer as clean drinking water was difficult to come by. Utrecht alone had roughly thirty breweries. These were almost all situated along the Oudegracht, which was, back then, connected to the North Sea through a tributary of the Rhine. Around 1930, the last breweries disappeared from Utrecht. Only in 1990 did the brewing tradition return to the Oudegracht (after 93 years of silence), when the Utrecht City Brewery settled in the vaults of City Castle Oudaen. While the Oudaen belongs to the world’s smaller breweries, it's a modern business. Each year, about 75,000 litres of beer are produced. The only steam brewery in Utrecht is situated in one of the four underground vaults which are located beneath street level inside the castle.