Himeji Castle, a UNESCO World Heritage Site, boasts the tallest, extant main keep in Japan. The elegant main keep and the sub-keeps are connected by corridors, forming a sturdy defense.

We then look at how castle's became stronger and more sophisticated, with the addition of stone curtain walls, massive keeps, towers (square, round and D-shaped), as well as powerful gatehouses ...

It is estimated over five hundred motte-and-bailey castles were built in the two years after the Norman conquest. Stone keep castles were often built on the same site as motte-and-bailey castles.