Mweelrea is the name given to a set of mountainous ridges that 'guards' the northern side of the mouth of Killary Fjord (the fjord marks the border between Galway and Mayo). At 816 metres, it is the tallest mountain in Connacht, and one of the trickier to climb. There are a few narrow steep ridges but mainly, one is nearly alway guaranteed some cloud on the top, making navigation difficult. I've climbed it a few times (it's one of my favourites) and the view (if you can get it) is well worth the climb. See http://www.monasette.com/archive/000968.html & http://www.monasette.com/archive/001146.html for accounts of hikes in Mweelrea.