High Quality Content by WIKIPEDIA articles! Lough Derravaragh (Irish: Loch Dairbhreach) is a lough (lake) in County Westmeath, Republic of Ireland, north of Mullingar between Castlepollard, Collinstown, Crookedwood and Multyfarnham. Knockeyon, 214 m high, one of the highest points in Westmeath, situated on the southeastern lake shore, dominates the surrounding countryside.