During the 5th century, Canterbury went into decline and its Roman institutions and buildings crumbled, although the city walls survived.
In 597, Augustine was sent to Kent by Pope Gregory I to convert the local population to Christianity.
Augustine established Canterbury Cathedral within the city, possibly because the walled site gave them additional protection or because it was symbolically important as a former Roman city.
Canterbury, now called Cantwaraburh, prospered and its population and trade increased.
Much of the land within the walls had become water meadows and farmland, and an palisade may have built around the cathedral and its precinct to form a secure inner stronghold.

In the late Anglo-Saxon period, the internal street layout of Canterbury was remodelled, but the line of the outer walls remained the same.
A cattle market was created outside the city to the south-east, and Newingate, later renamed St George's Gate, was inserted into the walls to allow easy access to it.
During this the period the main axis of the city shifted from the older line of streets running from London Gate and Riding Gate, to the new route between West Gate and Newingate.
A lane was built running around the inside of the walls, in a similar way to the intramural streets built around the same time at Exeter and Winchester.
Churches and chapels were built over the gates, including St Mary's above the North Gate; the Holy Cross over West Gate; St Michael's over Bargate; St Edmund's within Riding Gate; and, potentially, St George's Chapel over Newingate.
Canterbury's walls were mentioned by the early chronicler, Bede, in his history of England.

Despite Canterbury's walls, a Viking army successfully attacked the city in 835, killing many of the inhabitants.
Scandinavian raids recommenced from 991 onwards and in 1011 a Danish army demanded fresh tribute from the city.
The city walls were used to defend the city during an 11-day siege, and the chronicler Roger of Hoveden recounts how the attacking Danes were thrown off the tops of the walls to their deaths by the citizens.
Roger's account may be an exaggeration, but the story shows that the city walls were in sufficiently good condition for such a story to be considered plausible at the time.
After a fire broke out in the city, however, the Danes entered and pillaged Canterbury.
During the 5th century, Canterbury went into decline and its Roman institutions and buildings crumbled, although the city walls survived. In 597, Augustine was sent to Kent by Pope Gregory I to convert the local population to Christianity. Augustine established Canterbury Cathedral within the city, possibly because the walled site gave them additional protection or because it was symbolically important as a former Roman city. Canterbury, now called Cantwaraburh, prospered and its population and trade increased. Much of the land within the walls had become water meadows and farmland, and an palisade may have built around the cathedral and its precinct to form a secure inner stronghold.
In the late Anglo-Saxon period, the internal street layout of Canterbury was remodelled, but the line of the outer walls remained the same. A cattle market was created outside the city to the south-east, and Newingate, later renamed St George's Gate, was inserted into the walls to allow easy access to it. During this the period the main axis of the city shifted from the older line of streets running from London Gate and Riding Gate, to the new route between West Gate and Newingate. A lane was built running around the inside of the walls, in a similar way to the intramural streets built around the same time at Exeter and Winchester. Churches and chapels were built over the gates, including St Mary's above the North Gate; the Holy Cross over West Gate; St Michael's over Bargate; St Edmund's within Riding Gate; and, potentially, St George's Chapel over Newingate. Canterbury's walls were mentioned by the early chronicler, Bede, in his history of England.
Despite Canterbury's walls, a Viking army successfully attacked the city in 835, killing many of the inhabitants. Scandinavian raids recommenced from 991 onwards and in 1011 a Danish army demanded fresh tribute from the city. The city walls were used to defend the city during an 11-day siege, and the chronicler Roger of Hoveden recounts how the attacking Danes were thrown off the tops of the walls to their deaths by the citizens. Roger's account may be an exaggeration, but the story shows that the city walls were in sufficiently good condition for such a story to be considered plausible at the time. After a fire broke out in the city, however, the Danes entered and pillaged Canterbury.
Canterbury city walls