Cuilcagh

Cuilcagh () is a mountain on the border between County Fermanagh (in Northern Ireland) and County Cavan (in the Republic of Ireland). With a height of it is the highest point in both counties. It is also the 170th highest peak on the island of Ireland, and Ireland's only cross-border county top. Water from the southern slope flows underground until it emerges some miles away in the Shannon Pot, the traditional source of the River Shannon. The area is sometimes referred to as the Cuilcagh Mountains.

==Naming== The name Cuilcagh comes from the Irish Cuilceach, which has been translated as "chalky". However, the mountain is mainly sandstone and shale, covered with bog and heather. The cliff-edged summit surface of the mountain is formed from the hard-wearing Lackagh Sandstone which itself overlies the Briscloonagh Sandstone. "It is possible that the name refers to the limestone rock on the lower northern flanks, namely the Glencar and Dartry Limestone formations. Here a number of streams disappear below ground at swallow holes named Cats Hole, Pollawaddy, Pollasumera and Polliniska, all forming part of the Marble Arch cave system. If so, the name would mean 'calcareous' rather than 'chalky. It has also been called Slieve Cuilcagh in English, 'Slieve' being an anglicisation of Sliabh ("mountain").