Complex sentence: Caerleon is a site of considerable archaeological importance as the location of a Roman legionary fortress or "castra" (it was the headquarters for Legio II Augusta from about 75 to 300 AD) and an Iron Age hill fort.
Split into simpler sentences: Caerleon is a site of considerable archaeological importance as the location of a Roman legionary fortress or "castra". It was the headquarters for Legio II Augusta from about 75 to 300 AD, and the site of an Iron Age hill fort.