Created from nothing in 1921, after 26 of Ireland’s 32 counties wrested freedom from Britain, the border has never been loved by those who live along it. Partition divided families and farms, impeded business and travel, fuelled the birth of the Troubles in 1968. More than 3,500 people died before the Good Friday Agreement of 1998 put an end to the killing, in part by making this border — all 500 winding kilometres of it — almost irrelevant. Customs posts vanished. The British army withdrew. Northern Ireland remained firmly part of the United Kingdom, but in most day-to-day terms, the island became effectively one.

Now, after 20 years of peace, old scars threaten to reopen. Britain’s vote to leave the European Union will — if a hard “Brexit” ensues — leave the south of Ireland in the European Union, the north outside it. Security experts fear that a different regulatory regime would bring a resurgence in smuggling, organized crime, local protests and militant activity.

Yet the borderlands are still among Ireland’s best-kept secrets. To journey along the border is to discover the beauty of landscapes that few outsiders — even from Ireland — ever explore. There are ancient sites far from the usual tourist trails, and quiet villages and proud stone towns that were the ancestral homes of many early settlers in Canada and the United States. And talking to local writers, historians and residents reveals something curious: the idea that a border that few people wanted, and which currently exists in little but name, still endures in the imagination, not merely as a line of division but also as a common thread of identity.

“They should just call this region the borderlands,” says Shirley Clerkin, heritage officer for Monaghan, a border county in the southern Republic. “The border isn’t a line, it’s a place, north and south. If you ask anyone who lives along it where they’re from, they’ll say they’re from the border.”

The border has sometimes been hard, sometimes soft, but it has always been porous for those who don’t fear it. Writer and journalist Susan McKay, a native of Waterside, a Protestant area just outside Londonderry (as most pro-British Northern Ireland Protestants prefer to formally call Derry City), remembers how, even during the Troubles, her family maintained its tradition of holidaying across the border, on the beaches of Donegal. County Donegal has, in turn, always been Derry City’s main hinterland. Derry may be in a different country, but for Donegal people it is still their biggest town, a place to shop and work and party.

“Derry has always prided itself on its outsider status. It’s always seen itself as sort of cool in a way that Belfast is not,” says McKay. “It’s got this lovely old walled centre with views across to the Donegal hills and over the river, and now it’s getting new things like the boutique hotels on Bishop’s Gate and Shipquay. There’s a vibrant arts scene, with the Field Day theatre company and the Nerve Centre for youth. And it’s very lively at night.”

Walking tours of Derry’s famous walls cannily repackage the city’s fractious history — an unsuccessful siege by the mainly Catholic army of James II in 1689 and the birth of the Troubles in the Bogside area among them. A pedestrian Peace Bridge across the River Foyle, completed in 2011 with European funding, now joins a mainly Catholic city centre to the predominantly Protestant Waterside district, restoring some shared sense of civic ownership.

Yet in common with other border communities, Derry still suffers from poor road and rail links to the rest of the island, north and south. McKay cites talk from Northern Ireland’s Democratic Unionist Party, which supported Brexit, about building new transport links to “mainland Britain.” “They want to build a bridge to Scotland,” she says, “but they won’t build a decent road between Derry and Belfast.”

South of Londonderry, the border follows the River Foyle south before turning east, between the lake-splashed counties of Cavan and Fermanagh. This is drumlin country, a picturesque region of steep little clay hills. The word “drumlin” is used by geologists worldwide to describe these common post-glacial formations. It originated here, from the Gaelic droimnín, or “little ridge.”

At Clones, in County Monaghan, north and south become inextricably entangled. Driving southwest from Clones to Cavan, also in the Republic, the road crosses the border four times in 10 kilometres. Once patrolled by tense, heavily armed police of the Royal Ulster Constabulary, these crossings, now unguarded, betray themselves with signs welcoming you “back” to County Monaghan, “twinned with Prince Edward Island, Miramichi, New Brunswick, and Peterborough, Ontario.”

For many old settler families in Canada and the United States, these borderlands were a waypoint in a long westward migration. Some were already frontier folk — “Reiver” clans from another lawless border, the one between England and Scotland — when, in the early 17th century, they answered the call for a Protestant and British crusade to colonize Ulster, Ireland’s northernmost province. There, Ireland’s old Gaelic and Roman Catholic order was making its last stand.

This “Plantation of Ulster” gave birth to modern Northern Ireland by creating a loyalist Protestant majority in the northeast of Ulster. But Protestants were still not a majority in the province as a whole, much less the rest of the island. In 1921, as Ireland’s Catholic majority fought for independence, the Ulster loyalists sought a breakaway state of their own. In order to engineer a guaranteed Protestant majority, three Ulster counties which had Catholic majorities — Monaghan, Cavan and Donegal — were abandoned to the new Irish Free State. With them went large Protestant minorities. “We are the lost three counties here,” says George Knight, a Protestant historian, raconteur and tour guide from County Monaghan. “The same way that Dublin gave up on all the Catholics in Northern Ireland, the unionists in Ulster abandoned their brethren down here.”

The relics of Plantation are everywhere in Knight’s hometown of Clones. In 2016, he helped rediscover a long-lost 17th-century castle, hidden inside a ruined building on one of Clones’ back streets. “We might have guessed where it was,” he jokes. “It was on Castle Street.”

Little is known about Ireland’s history before Christianity arrived in the fourth or fifth century, bringing writing with it. Early Christian scribes were the first to record some of the myths, annals and sagas that survived from the previous long “Celtic twilight.” The greatest of these stories, the Cattle Raid of Cooley, was itself a border epic, centred in the eastern uplands where the modern frontier meets the Irish sea.

It was here, in the Cooley Mountains of County Louth (then part of the ancient kingdom of Ulster) that a chieftain owned a bull so fine that Queen Maeve of Connaught, the most westerly province, sent her army to steal it. Its warriors stricken down by a curse, Ulster could only muster one hero to defend it: Cú Chulainn. The elements of his legend — invasion, blood feud, intimate betrayals and desperate last stands — echo down through millennia of Irish history.

A later wave of invaders, Normans from England, arrived at the foot of the Cooley Mountains in the 12th century. To fortify the mouth of strategic Carlingford Lough, they built a handsome stone castle at Carlingford, now in the Republic. Thomas D’Arcy McGee, a Father of Canadian Confederation, was born near its ruin in 1825. His monument stands near the shore of the lough, gazing west toward his destiny.