[7][8] The original walls were built around 71 AD, when the Romans erected a fort (castra) occupying about 50 acres or 21.5 hectares near the banks of the River Ouse.

The point where the wall crossed the via praetoria is marked by a plaque in St Helen's Square near the Mansion House.

The Multangular Tower in the Museum Gardens is the most noticeable and intact structure remaining from the Roman walls.

The walls are almost certainly the creation of Septimius Severus; however, the Multangular Tower is probably a later addition of Constantine the Great around 310–320 AD.

[9] The foundations are concrete, atop which the tower extends having a rubble and mortar core between ashlar faced courses of small magnesian limestone blocks.

After the bridge, the King's Fishpool, a swamp created by the Normans' damming of the River Foss, provided adequate security for the city, and no walls were ever built in this area.

In the Middle Ages the defence of the city was further helped not just by the walls but on the rampart underneath and the ditch surrounding them.

The walls resume beyond the now canalised Foss at the Red Tower, a brick building which has been much restored over the years.

They continue south and west around the Walmgate area, terminating in another tower (Fishergate Postern), near York Castle, which was formerly surrounded by its own walls and a moat.

They climb past Baile Hill, take a right turn and proceed north-west parallel to the Inner Ring Road.

Near the railway station, they turn right again in a north-easterly direction, finishing at Barker Tower on the Ouse.

The walls were repaired during the English Civil War by Parliamentarians[13] as well as during the later Jacobite Risings[14] due to fears of an invasion from Scotland.

[16] In the northern area where you have views of the Cathedral, the walls were defended from interval towers which would have been higher than they are now after the Victorian restoration.

It stands almost on the site of porta principalis dextra, the north western gate of Eboracum.

The barbican, and a section of wall, were demolished to make way for the construction of St Leonards Place in the 1830s.

The southwest doorway has remained unchanged, but there was one to the west which is now marked by a low recess in the room's wall.

It was originally called Walbegate, the word Walbe possibly being an Anglo-Scandinavian personal name.

The lower section was built in the 12th century while the top storeys in the 14th; the original barbican was removed in 1826.

The upper two floors contain living quarters, which today are a museum known as the City Walls Experience at Micklegate Bar.

In the event of a siege, a postern could act as a sally port, allowing defenders to make a sortie on the besiegers.

Crane Tower) Records describe it as a narrow arch with round turrets to either side and is estimated to have been built around 1315.

Barker Tower) Located on the west bank of the River Ouse on Wellington Row just to the north of Lendal Bridge.

Its original use was to have a chain secured to it and the other end attached to Lendal Tower on the opposite bank.

It was replaced by the Great North of England Railway Company for the multi-arch construction seen currently.

It was converted in the 17th century to a water tower, though remains of the original structure can still be seen in the waterworks yard.

In 1972 the Royal Commission on the Historical Monuments of England documented all the towers of the city walls and assigned them a number.