Segedunum was a Roman fort in modern-day Wallsend, Tyne and Wear, England, UK. The fort lay at the eastern end of Hadrian’s Wall (in Wallsend) near the banks of the River Tyne, forming the eastern-most portion of the wall. It was in use as a garrison for approximately 300 years, almost up to 400AD. Today, Segedunum is the most thoroughly excavated fort along Hadrian’s Wall, and is operated as Segedunum Roman Fort, Baths and Museum.
The Roman wall originally terminated at Pons Aelius (Newcastle upon Tyne). Work began at Pons Aelius in 122AD and proceeded towards the west. Subsequently, in about 127AD, the wall was extended further east, possibly to protect the river crossing at Pons Aelius. A four-mile section of the wall east from the fort of Pons Aelius, passing through present-day Byker and ending at the new fort of Segedunum was built. The new section of wall was narrower than the sections previously built, being 7 feet 6 inches (2.29m) on a foundation of 8 feet (2.4m). Unlike the rest of the wall, the extension had no vallum. The fort measured 453 feet (138m) from north to south and 393 feet (120m) from east to west, covering an area of 4.1 acres (17,000m2). A wide ditch and an earth embankment surrounded the fort on all sides. It had four double gates with the east, west and north gates opening outside the wall and only the south gate opening within the wall. The wall joined to the west wall of the fort just south of the west gate. From the southeast angle of the fort, a 6 feet 6 inches (1.98m) wide wall ran down to the riverbank and extended at least as far as the low water level. There is evidence that there was an extensive vicus, or village surrounding the fort, including the area to the north of the wall. The original garrison of Segedunum is unknown, but in the 2nd century the Second Cohort of Nervians was stationed there. In the 3rd and 4th centuries the part-mounted Fourth Cohort of the Lingones occupied the fort, as recorded in the Notitia Dignitatum. Both units were 600 strong, 120 cavalry and 480 infantry.
The site of the fort now contains the excavated remains of the buildings’ foundation of the original fort, as well as a reconstructed Roman military bathhouse based on excavated examples at Vindolanda and Chesters forts. A museum contains items of interest that were found when the site was excavated and a large observation tower overlooks the site. A portion of the original wall is visible across the street from the museum, and a reconstruction of what the whole wall might have looked like. This eastern portion of Hadrian’s Wall was erected atop the Whin Sill, a geological formation which offers natural topographic defence with respect to invaders or immigrants from the north.