England: Deal Castle
Deal Castle was built in 1539 to protect the beach from the invading French. The design is quite interesting – the central 3-story citadel with guns is circular with 6 semicircular towers attached, each loaded with guns. Below is a platform with another 6 semicircular bastions, all loaded with more guns. The a layer of 53 more gun holes, then a moat. And the ocean is just 50 meters away.