Photograph of the portcullis at the entrance to the Byward Tower. The focal point of the image is the open doorway of the entrance through which can be seen the closed portcullis gate. There are smaller arched doorways in the walls of the passageway that leads to the entrance.  

The Byward Tower is the great gatehouse of the Tower of London's Outer Ward and was built by King Henry III between 1238 and 1272. It is located at the south-west corner of the Tower of London, adjacent to the moat. The Byward Tower has a series of defences which includes a drawbridge, arrow loops in the twin towers and two portcullises.