The Haus des Meeres (HdM, English: House of the Sea) is a public aquarium in Vienna, Austria.

The Haus des Meeres houses over ten thousand aquatic beings on an area of around 4,000 square meters (43,000 sq ft) inside a tall concrete flak tower built during World War II.

[2] The Haus des Meeres is managed by Aqua Terra Zoo, a private non-profit organization which, according to its web site, receives only marginal financial support from municipal authorities.

[4] After two years of experimenting with small seawater tanks Jäger built a large aquarium for public display.

[note 2] After the war the tower in Esterhazy Park was temporarily used as a hotel with 38 rooms in a bunker, and then converted to a fire station.

[9] The tenth floor, which recreates a flak turm control vault, houses World War Two exhibits and is open only on weekends, with advance registration of visitors.

The expansion had a side effect: the City of Vienna struck the "defaced" tower off the list of protected landmarks but enforced preservation of Weiner's billboard.

It is visible on the 55 euro cent commemorative stamp 50 Jahre "Haus des Meeres" issued by the Austrian Post in 2007.

[7][14] The global financial crisis caused an abrupt drop in visitor numbers of Viennese art museums.