The lake has an area of 0.2 square kilometres.
The phrase "inner" refers to the old city walls of Hamburg. The Binnenalster was the part of the lake that was "inside" the city walls. The lake was originally created to serve as a reservoir for a mill. As of 2008 the old city walls do not exist, instead two car and train bridges, the Lombardbrücke and the Kennedybrücke, span the river.
The building with tower is the Rathaus of Hamburg.
The Hamburg Rathaus is the Rathaus—the city hall or town hall—of Hamburg, Germany, it is the seat of the government of Hamburg, located in the Altstadt quarter in the city centre, near the lake Binnenalster and the central station. Constructed from 1886 to 1897, the city hall still houses its original governmental functions with the office of the First Mayor of Hamburg and the meeting rooms for Hamburg's parliament and senate (the city's executive).