1. Cardiff Castle was established within the walls of a mighty Roman fort (NPRN 301346) by William I of England in about 1081. The castle had a chequered history and fell into decline following the civil war. From 1776 a program of landscaping, clearance and reconstruction was embarked upon and from 1868 through to the 1920s the castle was transformed according to the fantastical Gothic plans of William Burgess and the Roman walls were cleared and reconstructed.

The great castle mound in the north-west corner of the fort was probably thrown up in the late eleventh century and its great shell keep was added soon afterwards, if not in the same operation. The fort was divided into two courts; the smaller inner court with the lord's apartments and offices, and the larger outer court where the county court and the knight's of the shire's houses were found. The Roman walls were retained about the inner court, but were covered by a great earthen bank around the outer court. The borough to the south was enclosed by strong walls and towers (NPRN 307774).

The castle apartments are on the west side of the inner court. The earliest fabric is early fifteenth century, but this is almost all the work of William Burgess and the towers and halls owe little to the medieval castle. The grounds are now municipal in character, but their earlier form is depicted in nineteenth century Ordnance Survey mapping (NPRN 301558).

Source: RCAHMW Glamorgan Inventory III.1a 'the Earlier Castles' (1991), 162-210

RCAHMW, February 2011

2. Parchmarks recorded during Royal Commission aerial reconnaissance on 22nd July 2013 revealed remains of building foundations throughout the interior of the castle, many of which have been previously excavated or documented in campaigns of geophysical survey. The line of one of the Roman roads crossing the interior was also visible, as was the concentric remains of a second world war barrage balloon site in the north-east corner of the lawned area (NPRN 419667).

T. Driver, RCAHMW, 2013.