This is the Peter Behrens AEG Turbine Hall in Berlin.
It is considered by many the first great 20th-century
expresion of pure functionalist architecture. Steel and
glass used on a very large scale, without decoration
of any kind for the first time. The two corner pillars
have only a binding and enclosing function and
therefore are made of another material: concrete.
Such a high honesty in the architecture in contrast
with the fake clouds displayed in the postcard is
somehow funny to me.