Dessau is where modernism put down roots. The Bauhaus school moved here from Weimar in 1925, and the buildings Walter Gropius designed for it — the Bauhaus Building, the Meisterhäuser, the Kornhaus — still stand as a UNESCO World Heritage Site. If you care about architecture and design, this small city on the Elbe is a genuine pilgrimage.
Beyond Bauhaus, the Garden Kingdom of Dessau-Wörlitz stretches along the floodplains east of town. This 18th-century landscape of English-style parks, neoclassical pavilions, and artificial lakes is another UNESCO site, and one of the best places in Germany for a long, aimless walk. Wörlitzer Park alone could fill a full afternoon.
Dessau itself is quiet — it was heavily bombed in the war and rebuilt in the usual East German concrete, so don't expect a picturesque old town. The draw is specific: two UNESCO sites of genuine world importance in a city most travellers skip entirely.