The availability of abundant water supplies has played a significant role in the development of Bern. There are more than 100 public fountains in the city, once the main source of household water and social interaction. Today, the fountains provide free drinkable water to residents and visitors. Originally the fountains were made of wood but were replaced in 1550 by stone works of art. Many of them depict allegorical figures such as Justice and the Ogre. Others depict biblical figures, for example, Moses and Samson. Some are in the middle of busy streets and act as traffic calmers. Water-themed walking tours are available.