The closer ones are a gate... the Jerusalem Tor and you can see the bridge there... the green area was a moat. On the far end some of the moat is intact. There was a Gasthaus called Valhalla across the street at the far end, but we used to buy a case of beer (warm) and tie a rope to it and let it sit in the cool water and we'd hang out there on the banks by the wall.
Büdingen Castle, a moated castle built by Lord Gerlach II von Büdingen in the thirteen century. Inside the thirteen angular wall ring are the main castle, the residence of the Lord, and the Gothic chapel.