Carlingford Lough in the context of "Irish border"

The Republic of Ireland–United Kingdom border, sometimes referred to as the Irish border or British–Irish border, runs for 499 km (310 mi) from Lough Foyle in the north-west of Ireland to Carlingford Lough in the north-east, separating the Republic of Ireland from Northern Ireland.

Border markings are inconspicuous, in common with many inter-state borders in the European Union. As the two states share a Common Travel Area and (as of 2021) Northern Ireland (the only exception within the UK and only in some respects) and the Republic of Ireland are participants in the European Single Market, the border is essentially an open one, allowing free passage of people since 1923 and of goods since 1993. There are circa 270 public roads that cross the border. Following the United Kingdom's exit from the European Union, this border is also the frontier between the EU and a non-member country. The Brexit withdrawal agreement commits all involved parties to maintaining an open border in Ireland, so that (in many respects) the trade frontier is the Irish Sea between the two islands. This de facto division of the United Kingdom is described, especially by Unionists, as "the Irish Sea border".

County Down (Irish: Contae an Dúin) is one of the six counties of Northern Ireland, one of the nine counties of Ulster and one of the traditional thirty-two counties of Ireland. It covers an area of 961 sq mi (2,490 km) and has a population of 552,261. It borders County Antrim to the north, the Irish Sea to the east, County Armagh to the west, and County Louth across Carlingford Lough to the southwest.

In the east of the county is Strangford Lough and the Ards Peninsula. The largest settlement is Bangor, a city on the northeast coast. Three other large towns and cities are on its border: Newry lies on the western border with County Armagh. Lisburn and Belfast lie on the northern border with County Antrim. Down contains the southernmost point of Northern Ireland (Cranfield Point) and the easternmost point of Ireland (Burr Point).

Newry River (Irish: An Rí; Ulster-Scots: Clanrye Wattèr), also known as the River Clanrye, is a river in Northern Ireland, flowing through counties Down and Armagh. The river passes through the city of Newry and empties into Carlingford Lough near Warrenpoint.

County Louth (/laʊð/ LOWDH; Irish: Contae Lú) is a coastal county in the Eastern and Midland Region of Ireland, within the province of Leinster. Louth is bordered by the counties of Meath to the south, Monaghan to the west, Armagh to the north and Down to the north-east, across Carlingford Lough. It is the smallest county in Ireland by land area and the 17th most populous, with just over 139,100 residents as of 2022. The county is named after the village of Louth. Louth County Council is the local authority for the county.

Lough Swilly (Irish: Loch Súilí, meaning 'lake of eyes') in Ireland is a glacial fjord or sea inlet lying between the western side of the Inishowen Peninsula and the Fanad Peninsula, in County Donegal. Along with Carlingford Lough and Killary Harbour it is one of three glacial fjords in Ireland.

Warrenpoint is a small port town and civil parish in County Down, Northern Ireland. It sits at the head of Carlingford Lough, south of Newry, and is separated from the Republic of Ireland by a narrow strait. The town is beside the village of Rostrevor and is overlooked by the Mournes and Cooley Mountains. Warrenpoint sprang up within the townland of Ringmackilroy (from Irish Rinn Mhic Giolla Ruaidh 'McIlroy's point'), and is locally nicknamed "The Point", which also represents the town's full name in Irish, An Pointe.

Warrenpoint is known for its scenic location, the Maiden of Mourne festival, the Blues on the Bay music festival, the passenger ferry service between Warrenpoint and Omeath and the nearby Narrow Water Castle. Warrenpoint Port is second in terms of tonnage handled by ports in Northern Ireland. It had a population of 9,091 at the 2021 Census.

Carlingford (from Old Norse Kerlingfjǫrðr 'narrow sea-inlet of the hag'; Irish: Cairlinn) is a coastal town and civil parish in northern County Louth, Ireland. For the purposes of local government, the town is part of the Dundalk Municipal District. It is situated on the southern shore of Carlingford Lough with Slieve Foy mountain as a backdrop, sometimes known as Carlingford Mountain. It is the main town on the Cooley Peninsula. Located on the R176/R173 roads between Greenore and Omeath village, Carlingford is approximately 27 km (17 mi) north east (by road) from Dundalk (15.6 km; 9¾ miles directly), 90 km (56 mi) north of Dublin and 11 km (7 mi) south of the border with Northern Ireland. Carlingford won the Irish Tidy Towns Competition in 1988.

Carlingford still retains its medieval layout noticeable by the narrow lanes and small streets. Tholsel Street is where the last of the medieval walled town's gates can still be seen, called "The Tholsel" which apparently was also used as a jail, on Tholsel Street itself there is still a 16th-century Town House known as the Carlingford Mint.

Cranfield Point (Irish: Pointe Chreamhchoille) is the southernmost point of Northern Ireland. It is located at the mouth of Carlingford Lough in the townland of Cranfield, County Down.

It was once the site of the Cranfield Point lighthouse, marking the entrance to the lough. Its poor position led to the construction of the Haulbowline Lighthouse situated in the middle of the entrance to Carlingford Lough. Cranfield Point Lighthouse subsequently fell victim to coastal erosion and collapsed into the sea during the 1860s. The lighthouse keeper's cottage remained and was later converted into a private residence that can still be seen as of 2007, identified by its characteristic tall black chimneys.