For the first time in centuries, walkers can now make their way along the length of Hadrian's Wall, which has just opened as a national trail. But why was the huge fortification built in the first place?
By Christine Jeavans
BBC News Online
It was on a visit to Britain in AD 122 that the Roman emperor Hadrian ordered a great wall to be constructed on the empire's northern frontier beyond which lay "barbarian" tribes.
Hundreds of men from three legions spent six years spanning the 80 Roman miles (73 modern miles) from Wallsend in the east to Bowness-on-Solway in the west.
The result was an impressive battlement, standing at least 15 feet (five metres) high and heavily fortified with "milecastles" along its length, garrisons, look out points and several large forts.
The wall runs 80 Roman miles from coast to coast
But for all this fortification, historians say it is too simplistic to think, like Hadrian's Roman biographer, that the wall was built "to separate the Romans from the Barbarians".
"Recent research suggests it was mainly a customs frontier, we shouldn't think of it in terms of 'cowboys and Indians'," says Roman historian Dr Mike Ibeji.
"It's Hadrian very deliberately saying 'these are the limits of the empire and we want to charge anyone from outside the empire a fat little tax if they want to come in and trade.
"It's a line of demarcation, garrisoned by auxiliary troops who police the area and regulate the movement of barbarian tribes along the frontier."
But more than that, he says, it was a symbol of achievement for the emperor.
Just as the Americans can say 'we've got smart bombs and you can't touch us', the Romans were saying to the local tribes 'we can build a wall 80 miles long'
"Hadrian had just taken over from a very aggressive emperor who had expanded the empire into Persia but it was now overstretched."
Normally a new emperor would have had a war and conquered a region to make his mark on the empire and to win admiration back home.
Hadrian realised he could not expand, says Dr Ibeji, but after a massive tour of his territories, he decided to construct a wall but not out of wood as previous walls elsewhere in the empire had been.
"Hadrian being Hadrian, it wasn't enough to build it in wood because it didn't have enough kudos back in Rome.
"He started off building it in wood and turf but rebuilt it in stone and it ends up a great and wonderful wall which took three legions to build and run it."
Jim Crow, senior lecturer in archaeology at Newcastle University agrees that the wall would have had a great impact - but on those living nearby.
"It's a symbol of Roman power; just as the Americans can say 'we've got smart bombs and you can't touch us', the Romans were saying to the local tribes 'you guys live in round huts - we come from a city with a million people and we can build a wall 80 miles long'."
There is some evidence to suggest that it was painted white, he adds, making it even more of an imposing sight in the landscape.
But Mr Crow believes that the way the wall was constructed also shows the problems the Romans were having with the native tribes, both to the north and south.
"It's the most heavily fortified border anywhere in the Roman Empire," he says.
"It is always said to be 15 feet high - and so it is, to the level where the soldiers were standing - but with a parapet on top that's more like 20 feet and there's a ditch either side."
On the north side, recent excavations have found evidence of big pits which are likely to have been filled with stakes - a typical form of Roman defence.
It was more a monument to what Rome was and what Rome was remembered as being
And to the south there was the Vallum a colossal ditch flanked by mounds of earth.
"This shows they were concerned about security to the south as well as the north," says Jim Crow.
"We should not think that south of Hadrian's wall was a demilitarised zone with no soldiers in it.
"There was a militarised zone running from the north of a line between Chester and York up to the wall, which indicates the Romans' insecurity about the area."
But while the wall was a huge achievement, by the time the Roman Empire fell in the 5th Century AD it was already largely obsolete.
"It was more a monument to what Rome was and what Rome was remembered as being," says Dr Ibeji.
"After the empire collapsed we had a whole bunch of people trying to still live Roman lives but without the infrastructure to do so.
"One leader even built himself a long house at one of the forts reusing some of the stone, trying to maintain the fiction."
And to Jim Crow the wall can be seen as a symbol of failure of the empire even when it was first built.
"The Romans used it as a symbol of power but you can turn that on its head and say it is a symbol that they never fully conquered Britain otherwise they would not have need the wall."