Aghla Beg is a mountain in County Donegal, Ireland. Of its two summits, one has a height of 564 metres, and the other, Aghla Beg South Top 602 metres. The mountain is the third-most northern and fifth-highest of the mountain chain, called the Seven Sisters by locals: Muckish, Crocknalaragagh, Aghla Beg, Ardloughnabrackbaddy, Aghla More, M…Aghla Beg is a mountain in County Donegal, Ireland. Of its two summits, one has a height of 564 metres, and the other, Aghla Beg South Top 602 metres. The mountain is the third-most northern and fifth-highest of the mountain chain, called the Seven Sisters by locals: Muckish, Crocknalaragagh, Aghla Beg, Ardloughnabrackbaddy, Aghla More, Mackoght and Errigal. The Seven Sisters are part of the Derryveagh Mountains.