In 2015 I had a summer break in Norfolk. It is such a historic county and I had the opportunity to visit a few Roman site whilst there. Included in that is what must be my second favourite Roman site of Burgh Castle.
Gariannonum, or Gariannum, was a Saxon Shore fort in Norfolk, England. The Notitia Dignitatum, a Roman Army “order of battle” from about AD 400, lists nine forts of the Saxon Shore in south and east England, among which one was called Gariannonor. It has been much discussed over the years in terms of spelling (Gariannonum, Garianonum, Gariannum), purpose (whether it really was intended for defence against Saxon raids), and location (whether Burgh Castle or the Caister-on-Sea site).
Caistor Roman fort
Gariannonum has usually been identified with Burgh Castle. However, modern reassessment of the Roman settlement 9 kilometres (5.6 mi) away at Caister-on-Sea has shown that it too had a military function. In Roman times, both sites lay on opposite sides of a large estuary (the remnant of which is Breydon Water). The identification of Burgh Castle as Gariannonum is uncertain, and the name could apply to Caister-on-Sea.
The name Gariannonum has been thought to derive from a Celtic root meaning "babbling river," which may refer to the River Yare at Burgh Castle, although the derivation is uncertain. The military function of Caister-on-Sea is also open to doubt. Both sites probably operated together and one, or possibly even both, were known by the Romans as Gariannonum.
The fort is roughly rectangular measuring (internally) approximately 205 m (673 ft) by 100 m (330 ft). The walls on the north, east, and much of the south side are largely intact, standing at a height of approximately 4.6 m (15 ft) and measuring up to 3 m (9.8 ft) thick at the base. They have a core of mortared flint rubble and an external and internal facing of prepared flint and red tile or brick in alternating bands. Against the outer face of the walls there are six solid bastions of pear-shaped plan spaced symmetrically, two on the south wall, one each at the north east and south east angles, one slipped from position on the north wall, and one below the south wall where it has fallen. The west wall has at some time in the distant past collapsed down the underlying hillside and into what was once an estuary but is now a marsh, and nothing of it is now visible. Breydon Water is all that is left of the estuary this fort once overlooked.
Coin and pottery evidence on the site indicates that the occupation of the fort dates from the mid-3rd century AD, with Roman occupation continuing up to the early 5th century AD when the integration of Roman and Saxon traditions appear.