Image of sunrise at Trim Castle in County Meath Republic of Ireland. Begun in 1172 and completed in 1224, Trim Castle is located on the south bank of the River Boyne in the town of Trim, County Meath. It is the largest Norman castle in Ireland. In the late middle ages Trim Castle marked the northern boundary of The Pale. It was used extensively as a set for the movie Braveheart.