There were two motte and bailey castles, Castle
Mound (at 40 foot high is one of the largest in England) and Red Castle
which is the earlier of the two having been erected at the end of the 11th
century. The wooden buildings were destroyed in 1174. Traces of earthworks
are visible.
Also in Thetford are the remains of the 12th century Thetford Abbey. Two miles to the west is Thetford Warren hunting lodge dating from 1400.