Wasserturm Ostkreuz, Water tower in Friedrichshain, Berlin, Germany

Wasserturm Ostkreuz is a 59-metre water tower beside Berlin Ostkreuz station, designed by Karl Cornelius and built 1909–1912 for the Royal Railway Directorate. Its shaft and steep octagonal cap are clad in glazed violet clinker brick, topped by a copper spire; the steel tank sits hidden in the cap, its underside at 40 metres. Access is through a masonry round-arched portal, inside via spiral iron stairs rising over seven galleries.

Built between 1909 and 1912 by designer Karl Cornelius, the tower was constructed to supply water for the expanding railway network. This timing coincided with Berlin's major push to modernize its urban infrastructure during the early industrial era.

The tower's name comes from the Ostkreuz station beside it, and its glazed violet clinker brick was chosen to shed the soot of steam locomotives washed down by rain. Water was pumped up from Rummelsburger See and fed the water cranes at Ostkreuz, Ostbahnhof, Lichtenberg and Rummelsburg stations.

The tower stands on railway land beside Berlin Ostkreuz station in Friedrichshain, not in Kreuzberg, and there is no public interior access; a woman who climbed it in June 2020 was injured and rescued by the fire department. It is best viewed from outside, from the station and surrounding streets.

The tower's steel tank sits at a standardised height of 40 metres, keeping water pressure constant so it could feed hydrants at Ostkreuz, Ostbahnhof, Lichtenberg and Rummelsburg stations. The water itself was pumped up from Rummelsburger See. The tank and hydraulic systems are not protected monuments and were slated for removal in any conversion.