Great Castle House, built in 1673, is now the home of the Royal Monmouthshire Royal Engineers (Militia), the oldest regiment in the British Army.
1673. aastal rajatud Monmouthi kindluse peahoone (Great Castle House) majutab tänapäeval Monmouthshire'i kuninglikku insenerirügementi, mis on Briti armee vanim rügement.