Rhuddlan Castle in Denbighshire

You're standing at Rhuddlan Castle, or Castell Rhuddlan, to use its Welsh name. Take a look at the shape of these ruins. The English king Edward I picked this spot in 1277, while he was conquering Wales. His master mason, James of St George, built a castle with two rings of walls, one inside the other. The clever part is the gates. Instead of sitting in the middle of the walls, they're placed at the corners. That gives the whole thing a diamond shape you won't find at any of Edward's other castles.