The ruined outer court of an Augustinian priory founded in 1136, established by canons fleeing Welsh raiders from the original Llanthony Abbey in the Brecon Beacons. What survives includes a fifteenth-century tithe barn and some late medieval storage buildings, set in grounds that now serve as a nature reserve.
It sits tucked away near the docks, easily missed, but worth the short detour if you're in the area.