If the harbour is Hamburg's hear t then the Alster is its soul. Dammed in the 13th century, today it gives the city a special kind of atmosphere and is an integral par t of the panorama. Which other metropolis can boast a lake in its midst? The Outer Alster is a basin that stretches over 160 hectares and has an average depth of 2.5 metres. Parks and other areas of greenery, which are filled with a number of statues, flank it. In the summer the Outer Alster is a popular place for sailing and rowing. If it is very cold in the winter, the lake can freeze over, which is always a cause for celebration for the locals. The Inner Alster Lake (18 hectares) is vir tually square-shaped. It was separated from the Outer Alster in the 17th century and is flanked by three promenades: the Ballindamm, the Jungfernstieg and the Neuer Jungfernstieg. In the summer a huge fountain sprays water to a height of 35 metres.