The Spree meanders through Berlin for exactly 47 kilometers. Since the Spree is a very slow river, it only covers about 17 kilometers a day, which means it spends almost three days in Berlin. This provides ample time to look around, count bridges, or listen to stories from an experienced city or river guide about events that have taken place on or along the Spree. These include cultural, political, and even criminal events from the past to the recent present. For example, it covers the smallest public ferry, a rowboat, the fisherman Karl Lupe who saved 138 people from death, the Friedrichshagen poet circle, the Köpenicker trial against Lieutenant Katte, a friend of the later Frederick II, the S-Bahn murderer in Rummelsburg, Fontane's egg house in Treptow, and the artificial island, now known as the Island of Youth.