The rivulet originates on the Róissear-gréine moor to the east of Cáistell-gréine from an underground well. It courses through the moor over a length of 745 metres, for a part through a small forested area, before confluencing with the Óimbhe hÓ to form the Óibhmhe Céifran. The rivulet is accessible by foot. Along its length runs a trail that originates at Cáistell-gréine railway station to the seaside, making it a popular landmark with hikers.