Canterbury's importance to the Romans lay in it being a port on the western side of the Wantsum Channel. The city walls are mainly Roman, dating from the end of the 3rd century, though they were repaired in the 14th century and strengthened with a number of towers. At least half of the city walls are visible on the eastern side of the city, as well as the city's West Gate which dates from 1380. The other three gates were destroyed in 1648. A wooden motte and bailey castle was erected in 1066 and the motte, known as Dane John, is still visible. The large keep was rebuilt in stone in 1100 and the lower half of it still remains, the top floor having been destroyed in the 19th century.
