Up until 1944 the Hansaviertel (Hansa district) was a wealthy area. The district was chosen as a test ground for modern architectural designs in 1957, when these buildings and tower-blocks (1,300 accommodation units for 3,500 inhabitants) surrounded by greenery were constructed for the Interbau International Architecture Exhibition (Internationale Bauaustellung Berlin). 53 architects from 13 different countries were involved, including Alvar Alto, Oscar Niemeyer, Egon Eiermann and Walter Gropius.