Enri Aimhreidh is better known for the foundation of a major castle above Newtonstewart. This appears to have been a significant building based on Norman fortresses such as Carrickfergus, Dundrum or Greencastle in County Donegal. The built remains we see today are the entrance to the structure which was flanked by towers similar to Greencastle. However the entrance then connected to a staircase more like that of a tower house before the top of the site was accessed. The castle was surrounded by a curtain wall with at least two projecting towers. It must have been an impressive sight.