It had a stone base and a stone wall. There were milecastles with two turrets in between. There was a fort about every five Roman miles. From north to south, the wall comprised a ditch, wall, military way and vallum, another ditch with adjoining mounds. It is thought the milecastles were staffed with static garrisons, whereas the forts had fighting garrisons of infantry and cavalry. In addition to the wall's defensive military role, its gates may have been customs posts.
A significant portion of the wall still stands and can be followed on foot along the adjoining Hadrian's Wall Path. The largest Roman artifact anywhere, it runs a total of 73 miles (117.5 kilometres) in northern England. Regarded as a British cultural icon, Hadrian's Wall is one of Britain's major ancient tourist attractions. It was designated as a UNESCO World Heritage Site in 1987. In comparison, the Antonine wall, thought by some to be based on Hadrian's wall (the Gillam hypothesis), was not declared a World Heritage site until 2008.
It is a common misconception that Hadrian's Wall marks the boundary between England and Scotland. In fact Hadrian's Wall lies entirely within England and has never formed the Anglo-Scottish border. While it is less than 0.6 miles (1.0 km) south of the border with Scotland in the west at Bowness-on-Solway, in the east it is as much as 68 miles (109 km) away.
Hadrian's Wall was 80 Roman miles or 117.5 km (73.0 mi) long; its width and height varied according to the construction materials available nearby. East of the River Irthing, the wall was made from squared stone and measured 3 metres (10 feet) wide and 5 to 6 metres (16 to 20 feet) high, while west of the river the wall was originally made from turf and measured 6 metres (20 feet) wide and 3.5 metres (11 feet) high; it was later rebuilt in stone. These dimensions do not include the wall's ditches, berms and forts. The central section measured eight Roman feet wide (7.8 ft or 2.4 m) on a 3 m (10 ft) base. Some parts of this section of the wall survive to a height of 3 m (10 ft).
Immediately south of the wall, a large ditch was dug, with adjoining parallel mounds, one on either side. This is known today as the Vallum, even though the word Vallum in Latin is the origin of the English word wall, and does not refer to a ditch. In many places – for example Limestone Corner – the Vallum is better preserved than the wall, which has been robbed of much of its stone.