Himeji Castle was registered on UNESCO's World Heritage list in 1993. It is also known as the White Heron Castle and represents Japanese castle architecture at its highest, with almost all of the castle structure still intact from its original construction in the early 1600's. The nickname of white Heron Castle comes form the graceful appearance of the white plaster walls. The castle grounds are divided into inner-and-outer-walled zones, with gates built around maze-like spaces to confuse enemies, and a double moat for extra protection.