The Binnenalster, or inner Alster lake, is the smaller of the two artificial lakes at the heart of Hamburg, enclosed on three sides by the city's main shopping streets and the Jungfernstieg promenade. The Alsterfontäne, a single jet of water rising sixty metres in the lake's centre, runs from April to October and is illuminated at night.
In winter, when the lake freezes hard enough — perhaps one year in five — locals decamp en masse onto the ice for the Alstereisvergnügen, an impromptu festival of mulled wine stalls, fairground rides and food carts. Year-round, a small fleet of white passenger ferries does the round trip from the Jungfernstieg landing — the cheapest way to get a sense of the city from the water.