Inside the church of St Mary the Virgin (which is open during the day) there are some lovely wall-paintings. Amazingly, these date from around 1230; in Medieval times all churches were beautifully decorated inside. It is unusual to see so much remaining, as such paiintings have usually been destroyed or defaced beyond repair over the centuries.
The walls of the Roman town are obvious, but if you look closely at the church (especially on the south side) you can see lots of Roman brick and tile which was used to build it. There's a Roman pillar and its base in the churchyard too; you'll pass it if you walk round the church.
The church is (strangely ) on Church Lane. You'll find it if you follow the walls, or cross the middle of the Roman site on the 'Drove'.