Einstein Tower

Erich Mendelsohn designed the Einsteinturm in 1919 and it was finished in the early 1920s: a white tower with almost no straight lines, windows sunk into rounded hoods, the whole thing looking poured rather than built. It is in fact mostly brick, rendered smooth to imitate concrete, and that shortcut is why it has cracked and been repaired ever since. The purpose was entirely serious. A solar telescope at the top feeds light down a vertical shaft into a laboratory in the base, built to look for a shift in the sun's spectral lines predicted by general relativity. It remains a working solar observatory, which is why the inside opens only on guided tours.

What you actually see

• The tower itself - Mendelsohn's curved white form, one of the few built works of architectural expressionism.
• The dome - the mirror housing at the top that feeds sunlight down the shaft.
• The Telegrafenberg - a wooded hill of observatory buildings and research institutes, free to walk.
• The Great Refractor - the domed nineteenth-century telescope standing nearby on the same hill.

When to go

The hill and its paths are open all year and cost nothing to walk. Interior tours are scheduled rather than continuous, run mainly in the warmer half of the year and are usually in German, so check dates and book, because groups are small. Autumn gives the best light on the white render, and the beech woods around the science park turn well.

Honest expectations

You cannot simply walk in. The tower still works, so the interior is off limits without a booked tour and most visitors see the outside only. The render is patched and stained between restorations and looks tired at close range. It is a twenty-minute climb from Potsdam station, there is no cafe on the hill, and the other research buildings are closed to the public.

Nearby

Potsdam's old town and Dutch Quarter, and the parks and palaces of Sanssouci across the city.