Glangevlin or "The Forked Glan" is situated in the North West of Cavan, surrounded by the Cuilcagh Mountains and bordering the counties of Leitrim and Fermanagh.  The early inhabitants reached her possibly 5000 years ago, when tribes such as the Tuatha de Danann, the Formorians, the Milesians and the Celts found their way up the rivers Erne and Shannon, proof of this can be seen in the form of the dolmens, ringed forts, caiseals, passage graves and lake dwellings located in the area.  The numerous caves and underground passages provided a natural home for these early settlers.  The Ringed Forts were built as a defense against the wolves and eagles during the bronze age and were even used up to the 12th Century and even later.  They were built of clay, stone and bushes. 

The Tuatha de Danann are reputed to have settled in Derrynatuan where a famous smith called Gaibhne lived and made swords for Balor of the Mighty Blows who lived on Tory Island off the coast of Donegal.  Gaibhne also owned a famous cow "An Glas Gaibhleann".  This cow is reputed to have supplied the whole of Breffni with milk.  She could fill any vessel regardless of size.  The cow took off in a rage and leaped out through the mountain making a division in it which is now called "Glan Gap".  The cow landed with Balor of the Mighty Blows on Tory Island.

The Shannon derived it's name from Sionna the daughter of Lodon who was the son of Ler (the great sea god).  Sionna became filled with an unholy desire for knowledge, which at the time was the possession of man alone.  She dwelt in the land uner the wave and in that land was Connla's well with nine sacred Streams running from it and nine sacred Hazels growing round the margin.   These were the Hazels of Science, Poetry and Knowledge.  In the well lived the Salmon of Knowledge which fed on the hazel nuts so that whoever would eat the salmon would have all the knowledge in the world around him.  Sionna went to the well and tried to catch the salmon.  The salmon leaped and lashed it's tail in rage and the water of the well overflowed and swept Sionna into the "Land of the Mortals" through a hole in the earth which was forever to be associated with her name and known as "Lug-na-Sionna" or the "Shannon Pot".