By John Thorne
BBC North of England correspondent at Hadrian's Wall
It cost £6m and took longer than the Roman legionnaires took to build Hadrian's Wall - but the 84-mile (135-kilometre) path in its shadow is now open.
This unbroken, signposted national trail is a breath-taking challenge linking the Irish Sea at Bowness on the Solway Firth, across the neck of Britain to Wallsend on the river Tyne.
Hadrian's Wall, built on the emperor's orders to separate the Romans from the barbarians, is a sophisticated piece of ancient engineering.
Built of stone and turf, five metres (15 feet) high and three (9 feet) wide, the ruins of the mile castles, the forts and watch turrets and can still be seen.
And the landscape is as wild and frontier-like as it was 2000 years ago.
Rolling hills and heather-covered moors are the backdrop.
Only a few isolated farms and the odd hamlet break the clean wide-open windswept border country.
Tourist businesses are welcoming the extra 20,000 walkers expected to attempt the trek each year.
But others warn the wildlife and tranquillity that make the wall an international heritage site could be destroyed if the fragile monument is invaded.
On Friday to mark the opening, groups of re-enactment enthusiasts dressed as
Roman centurions marched along part of the wall near the settlement of Twice Brewed.
Now the long trail is open to walkers and ramblers.
A stamped passport will prove to doubters the trek has been completed.
The wall runs from the west of Cumbria to Wallsend
The invigorating northern winds never stop blowing here. You wrap up and wear waterproofs whatever the season.
But the challenge will be popular.
The six-year project has demanded much diplomacy along the way.
Landowners had to be persuaded, bypasses for unique archaeological sites had to be navigated.
There is an extra four miles of pathway away from the wall to accommodate objections.
But in the wake of the devastation brought to the area by the foot-and-mouth epidemic, this trail signals an economic re-awakening for an area that delicately balances its isolated ancient beauty with the daily reality of having to earn a living.