A short walk up the hill from the abbey, almost lost in a suburban graveyard, sits the smallest of Canterbury's three UNESCO sites. St Martin's is a low, modest stone church of no obvious importance until you start reading the masonry: the chancel walls contain Roman brick and tile, and parts of the structure are almost certainly older than the arrival of Augustine in 597.
The building was probably the private chapel of Queen Bertha, a Frankish Christian princess who married the pagan king of Kent in the 560s — her presence in Canterbury is essentially the reason the city ended up as England's ecclesiastical capital. The church is still active; opening hours are limited and best confirmed in advance, but the graveyard is worth a wander even when the door is shut.