Cardiff's great keep rests majestically on its medieval motte. Most likely, the Romans built earliest settlement at Cardiff in the mid-first century AD. A site of great strategic value along the extensive network of Roman roads in Wales, Cardiff sat along the main link between Caerleon (with its wonderful, virtually intact, amphitheater) and Carmarthen (where another, less well- preserved, amphitheater was built). The Romans constructed a 10- acre fort on the spot where the castle now rests.

The first Norman castle was built on the site in about 1091, by Robert Fitzhamon, Lord of Gloucester and one of the Conqueror's favored followers.