The Moritzburg is a late-15th-century brick fortress built by the Archbishops of Magdeburg as a residence and stronghold. It was wrecked in the Thirty Years' War and stood as a ruin for two centuries; the open ruin was finally enclosed under a striking modernist roof of folded aluminium plates in 2008, by the Spanish architects Nieto Sobejano.
Today the castle holds the Saxony-Anhalt state art museum, with strong collections of German Expressionism (Kirchner, Nolde, Marc), early-20th-century photography, and modern sculpture. The combination of medieval shell and contemporary roof is genuinely impressive, and the exhibitions are first-rate. Allow at least two hours.