Ardfad Castle is situated on the Isle of Seil or Seil Island as it is more commonly referred to. There is very little remaining of the castle but it was once the seat of the MacDougalls of Ardencaple. The remains are situated on a prominent position at Ardencaple bay about 500 feet from Ardfad farm house.
The castle was built of stone and lime and was of a very substantial nature. It stood in a defensive and imposing crag and would have been very difficult to attack. The lower part of this castle was adapted to fit the contours of the existing crag that it sits on. The castle has two easily recognisable round corner towers, one on the east and one on the west side of the structure. There are defensive slits in between.