A former library
Berlin's Dorotheenstraße boasts a large number of historic architectural highlights: one of the least conspicuous (and therefore most overlooked) is the former university library building located at number 28.
Dating from 1874, it was constructed in brick in the Bauakademie tradition. In 1922 the library collection was relocated to a larger site, and during the Cold War era, the building housed the GDR's Department of Industrial Research.
Currently used as a seminar centre by Humboldt University's Art History department, the site can usually be accessed by the public and is worth visiting to view a very specific feature.
The original cast-iron staircase easily ranks as one of the most beautiful architectural features anywhere in the city, and although, sadly, the rest of the interior has been almost entirely stripped of its period fittings, this wonderful work of art makes a visit worthwhile.
More impressive (and far more atmospheric) than you'd perhaps expect, this dimly lit remnant of Berlin's past really is a hidden gem.
A former market hall
Alte Universitätsbibliothek (old university library): Dorotheenstrasse 28, 10115 Berlin