As a remnant of 17th-century county limits, the border's physical profile indicates that it follows many watercourses but only in the highlands of the Cavan-Fermanagh section could the border be said to accord with any significant physical impediments to movement. There are around 270 road border crossings, with some roads traversing the border several times. Similarly, before its closure in 1957, a section of one railway line between Clones, County Monaghan and Cavan crossed the border six times in eight miles, initially with customs checks at each crossing.