St Peter's Church in Monkwearmouth stands near the north bank of the Wear, partially enclosed by the university campus. The west wall and tower of the original 674 AD monastery church survive intact — the stonework is Anglo-Saxon, with the characteristic long-and-short quoins and small round-headed windows of the period. The church is still in use as a parish church, which makes it a living building rather than a ruin.
The interior has Roman and early medieval stonework built into the fabric, and there are carved friezes that are among the finest surviving examples of Northumbrian stone carving. The church can be visited independently when open (check the parish website for hours). St Peter's is often overlooked in favour of more visually dramatic sites, but for anyone interested in early medieval history it is the most significant building in Sunderland by a considerable distance.