Alster and its mouth at Binnenhafen, is called Alsterfleet, as part of a network of inner-city canals, including Bleichenfleet, Herrengrabenfleet, Mönkedammfleet, Neuerwallfleet and Nikolaifleet. Alsterfleet is regulated by two locks at Rathaus/Rathausmarkt and Baumwall, the latter protecting it from the Elbe tide. History Hamburg was founded at the mouth of the Alster river in the 9th century and used it as a port. The water was used to flood the moats of the fortifications. The Alster has been dammed since 1190, originally to power a watermill. In 1235 a further dam was built for a second mill, which changed the shape of the river to be like a lake. In the 15th and 16th century, an Alster canal was built to connect Hamburg with Lübeck. The canal was about long and built from the Alster to the Beste, a tributary of the Trave river, at Sülfeld. Because of the difficulties in holding water, especially near marsh areas, the long waterway from Hamburg to Lübeck was navigable from 1529 to 1550 only. Hamburg expanded along the shores of the Alster, and several locks were constructed to make the river navigable. Until the 19th century water transport with barges were used up to the town of Kayhude. The barges—transporting building material, fuel, and foods—were staked or hauled. Economy The Alster is navigatable some 9 km upstream from the mouth. Alster Touristik GmbH (ATG), a subsidiary of the Hamburger Hochbahn, provides public and touristic transport on a fleet of Alster ferries in the city of Hamburg. Along the entire course within Hamburg, rowing or paddle boats are available for rent. Ecology In general, the Alster is assessed to be clean. Hamburg's Alster and its lakes and canals are famous for its white swans, cared for out of public funds since the 16th century. Legacy The Alster basin was an important model for the design of the Charles River basin, constructed in the early 20th century. Throughout much of Germany, an Alsterwasser (literally: "Alster's water") is the name for a type of shandy, a concoction of equal parts of beer and lemonade. The river inspired the Hamburg-born composer Oscar Fetrás to compose the popular waltz "Mondnacht auf der Alster" (in English: "Moonlit Night on the Alster"). Hamburg's largest aquatic center, the Alster-Schwimmhalle, is named after the river. See also List of rivers of Schleswig-Holstein List of rivers of Hamburg List of bridges in Hamburg