evidence: Ireland is an island located in the North Atlantic Ocean. In terms of size, it is the second largest island within the British Isles. Additionally, it ranks as the third largest island in Europe and twentieth in the world in terms of size. Politically, the island is divided between the Republic of Ireland and Northern Ireland, which is a part of the United Kingdom (UK). The Republic of Ireland, which is also known simply as Ireland, covers five-sixths of the island. Ireland is bordered by only one nation, which is the United Kingdom (Northern Ireland). Sometimes referred to as the Irish Border, the Republic of Ireland–United Kingdom (Northern Ireland) border runs for about 310 miles from Lough Foyle (northern side of Ireland) to Carlingford Lough (northeastern side of Ireland), separating Ireland from Northern Ireland. [...] The shape of the Ireland border is extremely irregular due to the well-established borders of the different counties. Additionally, there is no official documentation that explicitly defines the border. Instead, it is implied in the 1920 Government of Ireland Act, which infers the territory of Northern Ireland. One of the most noticeable features of the border is its irregularity. For example, the length of the border between Lough Foyle to Carlingford Lough is four times longer then it would be if it was a simple straight line. In total, there are about 200 different border crossings, and some roads cross the border more than once. In fact, one railway line that was closed in 1957 traverses the border six times.