its day, Hadrian’s Wall in northern England was an imposing barrier.

Strung across the narrow neck of the island for more than 70 miles at a height of up to 15 feet and manned by legionnaires and recruits, it was a clear announcement to first-century denizens of Britain that they had come to the northern reaches of the Roman Empire.

It’s an image of long-lost imperial power modern tourists would do well to remember when they arrive at the wall to find it guarded by sheep and easily scaled by even the least athletic of visitors.

With just a vestige of its former strength remaining after almost 2,000 years of age and erosion, the wall is still a stark reminder of the ingenuity and reach of the Roman Empire and a piece of British antiquity.

But after so much time, myth and misinformation have overgrown parts of the truth about the wall — for instance that it still marks the northern English border, or that it was built to repel Braveheart-like invaders. The wall, as everyone knows, was built to keep Kevin Costner out of Scotland.

It’s a statement that may sound funny, but it touches on a couple of pieces of lore about the wall that are, in fact, true.

The first is that Costner actually did become inextricably linked to the wall when it was used in an early scene of “Robin Hood: Prince of Thieves” in the early 1990s as the location for the hero’s fight with some soldiers.

Another myth is that the wall has anything to do with Scotland at all — false, because there was no country known as Scotland at the time nor an “England,” for that matter (the two nations would form later).

At the time of the Roman conquest of Britain, the northern end of the island was inhabited by a group of tribes collectively known as the Caledonians, one of which — the Picts — proved a frustrating enemy for the Romans when Emperor Hadrian was dealing with unrest throughout the empire.

So, in 122 A.D., rather than wage a costly campaign to subjugate the northern tribes, he decided instead to mark out his territory and reduce the Pictish threat by building the wall across the slender throat of the island, relegating the Picts to their territory in the north.

Today, large sections of the wall made out of stone (other parts were made of turf) still stand and can be toured by the public. The sites also include some of the larger structures left by the Romans.

One of the best preserved is Birdoswald Fort near Carlisle in northwestern England, a former stronghold and training camp for occupying soldiers now set in undulating countryside between small English farms.

Reached by a set of narrow, winding country roads, the fort is broken into two sections. The first is the modern tourist portion (3.80 pounds to enter), including a snack and gift shop and two-story informational walk-through exhibit explaining the history of the structure and the construction of the wall. Outside are the ruins of the old fort and indoor training area, with more displays about life in the structure and the evolution of the property after Roman times.

It’s mainly just some excavated wall foundations and reconstructed beams showing the location of columns and pillars in the original building, but, combined with the exhibit and displays, it does paint an interesting picture of life on Hadrian’s Wall almost 2,000 years ago.

And there is, of course, a well-preserved portion of the wall running along the front and around the fort, now reduced to a tourist-friendly height of about 6 feet in many places.

Together, they make a worthwhile stop for those who have heard of the wall, are interested in British history, or are just in the neighborhood enjoying the countryside. For Costner fanatics, however, you’ll have to go somewhere else to stand in the actor’s footsteps. The scene was filmed at a place called Sycamore Gap in Northumberland, miles down the wall.