The 16th-century Spandau Citadel, on a little island in the Havel River, is one of the world's best-preserved Renaissance fortresses. With its moat, drawbridge and arrowhead-shaped bastions, it is also a veritable textbook in military architecture. These days, the impressive complex multitasks as museum, cultural venue and wintering ground for thousands of bats. Climb the 30m-high Julius Tower for sweeping views. Top international artists perform at the Citadel Music Festival in summer.
