Hadrian’s Wall, the ancient marvel that snakes through northern England, quite rightly steals the show when it comes to the frontiers of Roman Britain. It’s a spectacular sight, rolling poetically over hillsides and serving up ruins of fortifications for all to see.

It once reached up to 4m in height and spanned an impressive 73 miles, and today boasts impressive remains with large portions of the original stone wall still intact. Its enduring presence, however, overshadows the true frontier that the Romans, those wily conquerors who built one of the world’s largest empires by the 2nd Century AD, constructed around 100 miles to the north.

It’s easy to see why there’s a lingering misconception that the Romans never made it past Hadrian's Wall, let alone into Scotland: it’s much neater and tidier to think that they stopped their foray at the tangible, man-made line that meanders through Northumberland and Cumbria. After all, the Romans were resident at Hadrian’s Wall for close to 300 years, defending their empire’s boundary and embedding themselves in the region. But the story of Rome’s north-west frontier far from ends there, for it was the Antonine Wall that, albeit briefly, held the title of the wildest edge of the empire.

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I grew up in Edinburgh, so this ancient monument rested right on my doorstep. But I had little awareness of its presence, which is mind-boggling when you consider that it was such a remarkable feat of engineering. It stretched some 37 miles from the Firth of Forth to the Firth of Clyde across central Scotland, and was built by the very legionnaires stationed there nearly 1,900 years ago. What’s more, today it’s one of Scotland’s six Unesco World Heritage sites, listed as part of its ‘Frontiers of Empire’ series, although arguably the least well known.

This could, in part, be down to the fact that, unlike its sibling to the south, there isn’t that much ‘wall’ to see. Originally one continuous barrier of earth and clay, it rose as high as 3m and was lined to the north by a great defensive ditch as much as 5m deep. Its layout was similar to Hadrian’s Wall, sprinkled with forts, gateways and watchtowers, but the Antonine Wall never benefitted from the addition of stone to the same extent, ensuring fewer remains. Today, unlike the solid sections found at Hadrian’s Wall, the remains comprise mainly of disjointed turf mounds and complex earthworks.

The Antonine Wall’s lack of celebrity status is also possibly due to its short lifespan. Although its year of completion remains debated (suggestions range from 142 AD to 150 AD), it’s generally accepted that this huge structure was abandoned within two decades.

What is certain, as Dr Louisa Campbell, postdoctoral fellow in archaeology at the University of Glasgow told me, is that the wall was a show of force, “a massive and labour-intensive physical presence”.

“The wall would most likely have been perceived as an intimidating structure and a hostile imposition to the cultural landscape, separating groups stretching back many generations,” she said, concluding that it was “unlikely to have been particularly welcomed by the locals”.

Unsurprising, really, when you consider that these locals resided in a land ruled by warriors and tribes deemed to be beyond the grasp of Rome. Despite various incursions, encampments and even some mutually beneficial trading relations, Caledonia, the Roman term for the unconquered lands to the north, remained a thorn in the side of many an emperor. The Antonine Wall marked the outer limits of what Rome saw as civilisation. What’s more, it was an uncommon one at that.

The Antonine Wall gives us rare insights into the Roman Empire’s attempts to control the edges of its world

“Built frontiers were quite unusual in the Roman world as the army typically relied on natural boundaries such as rivers or mountains,” said Dr Fraser Hunter, principal curator of Roman Collections at the National Museum of Scotland in Edinburgh. “The Antonine Wall, therefore, gives us rare insights into the Roman Empire’s attempts to control the edges of its world.”

Speculation continues about precisely why it was abandoned. “This was a difficult edge of the empire,” Hunter stated, “partly from the landscape, partly the hostility which they encountered in places, but also from the logistical point of view, meaning that extended supply lines were needed.”

Campbell agrees. “A combination of pressures elsewhere in the empire, less receptive locals, challenging terrain and environmental conditions probably contributed to Rome’s decision to withdraw from the Antonine Wall and re-garrison the previous frontier at Hadrian’s Wall,” she said.

The story of the Antonine Wall has not been completely lost. The Hunterian Museum at the University of Glasgow, Scotland’s first public museum, hosts a permanent exhibition on the Antonine Wall, displaying treasures from everyday items, such as ancient leather shoes, jewellery and coins, to carved distance stones, which marked the completion of sections as it was built. Campbell, who’s worked closely on many of the Roman exhibits here, hails it as “an outstanding collection of objects”.

In addition, there are 47 named sites along the route for travellers to explore, although unsurprisingly not all of them were created equal given the wall’s lack of solid stone credentials. I planned a route westwards by car from Edinburgh to take in some of the must-see sections.

It was always going to be an interesting recce: for starters, the wall’s route through Scotland's central belt covers much lowland territory that was at the heart of the Scottish Industrial Revolution. This takes anyone on a quest to follow the Antonine Wall through areas scarred by heavy industry, such as former coal and oil shale mines and past old ironworks. Interestingly, the ruins run parallel to some of the region’s major arteries including the Forth and Clyde canal, walker’s paradise The John Muir Way, and the main railway line between Edinburgh and Glasgow, proving that this stretch continues to be as important today as it was to the Romans.

My first stop was the town of Falkirk, around 26 miles west of Edinburgh, which stood out as a hotbed of remains with a number of different sites in quick succession. “I have a soft spot for the wall in Callendar Park, as it survived the urban sprawl of Falkirk,” Hunter had confided to me. Indeed, the park, which surrounds the museum at Callendar House, hosts a generous portion of the rampart and ditch, and provided me with my first excitable glimpse of the Antonine Wall. Inside Callendar House, there’s also a small exhibition detailing the history of the Antonine Wall under the expert eye of local archaeologist Geoff Bailey.

Less than three miles from Callendar House is Watling Lodge, where along a rather unprepossessing B-road, the tell-tale rise and fall of the ditch crawling over a low-lying hill was clear to see. Also in the area is Rough Castle. The remains of this once-upon-a-time fort are widely lauded as the jewel in the crown of the Antonine Wall, easily accessed by a path from the Falkirk Wheel (another, more contemporary, engineering success story).

Although Rough Castle was the second smallest fort along the wall, Bailey said, “it has everything to give the impression of what a fort looked like.” And it’s instantly obvious why it’s so revered. Whether walking along the boggy bottom of the ditch or high on the ridge of the rampart, the sheer scale is overwhelming. Standing on a damp mossy section of rampart looking across to the west of Scotland, I couldn’t help but wonder how far from home those legionnaires must have felt in this savage outpost prone to bouts of bad weather and hostility from ill-tempered natives.

A couple of miles further west, I came to the site at Seabegs Wood, which reared up around a bend in the road leaving little time to pull into the parking space. Here, it’s all about the Military Way, the wide, arrow-straight service road that ran behind the wall, whose remains can still be seen.

Eight miles on, a short walk up a sharp, steep hill revealed why Bailey asserted that the site at Croy Hill was “visually the most attractive section where you’ve got the crags”. As well as splendid views over the valley to the west, these dramatic crags show where the ditch was sheared through the rock – no mean feat nearly two millennia ago.

Things got higher still at nearby Bar Hill Fort. “Bar Hill is a place of exceptional beauty,” Campbell said, “as it’s the highest point along the Antonine Wall and provides amazing panoramic views across the surrounding landscape.” That it does, as well as a brief, thigh-burning hike up to its ruins, which include the stone remains of a well and the outline of a bathhouse.

The highlight, however, resided in the grounds of a small park tucked along a busy main road in the well-to-do neighbourhood of Bearsden, just a few miles north-west of Glasgow. Behind a low wall sits the more substantial remains of a Roman bathhouse, a somewhat surreal thought when you consider legionnaires once relaxed in the steam in this spot now enveloped by a 1970’s housing estate.

Of course, this cherry-picked approach to experiencing the Antonine Wall was only ever going to be an introduction. It gave me a flavour of what to look for and showed how addictive hunting down sections can be; no wonder there are experts and enthusiasts championing this forgotten frontier as a major attraction.

The story of the Antonine Wall may be more of a short read than a full-length feature, but it’s one that should be spoken of in harmony with its peer, Hadrian’s Wall. It has left a legacy of intrigue, archaeology, history, walks and activities – proof enough that it was, for a time, a pivotal frontier of the mighty Roman Empire.

“The wall is a lovely example of Rome’s endeavours to control what is now Scotland and the challenges the empire faced,” Hunter said. “It was an experiment – a massive-scale engineering exercise to try to separate Roman from non-Roman worlds.”

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