Einstein Tower

The Einstein Tower on the Telegrafenberg in Potsdam is a solar observatory built between 1920 and 1922, and one of the key works of German architectural expressionism. Erich Mendelsohn designed it as an almost organic, sculptural body in concrete and brick - a form intended to show off the new material, but technically so demanding that many details had to be plastered over afterwards. Inside, the spectrograph was meant to test Einstein's theory of relativity by analysing sunlight. The observatory is still in scientific use today, operated by the Leibniz Institute for Astrophysics Potsdam; the exterior can be visited freely, while the interior opens only on a few annual open days.