Spandau Citadel in Berlin

You're standing at the Spandau Citadel, one of the best-preserved Renaissance fortresses in Europe. It sits on an island, close to where the Havel and the Spree rivers meet. Take a look at the shape of the walls. Those sharp, pointed bastions are an Italian design, made to give attackers a very hard time. You get in across the water through the gatehouse, where a drawbridge once kept unwanted guests out.