Caisleán Uí Bhriain (O’ Brien’s Castle) was built in the 14th century. It was constructed within a more ancient Ringfort called Dún Formna, which is thought to date from 400BC.
In addition to fantastic views of the island, there is a marvellous vista from the Cliffs of Moher, sweeping left to the Burren, across Galway Bay to the 12 Pins of Connemara and out west to Inis Meáin and Inis Mór. On a fine day you can even see the Kerry mountains in the distance. It is well worth bringing up your camera especially for a spectacular sunset.
The castle is a rectangular keep which was built by the O’Briens. They were a Co. Clare clan who ruled the islands and much of Clare in medieval times. From this castle they could control the shipping routes into Galway and are reputed to have run a protection racket.
Due to its strategic location, the castle was subject to a lot of competing interests. It was taken by the O’Flahertys around 1582, and was in use until it was supposedly captured and broken down by Cromwell in 1652.
The original doorway was into the first floor, accessed by an external wooden stairs. Inside was a hall occupying the entire first floor, with an intramural stairs in the SW wall which led up to the parapets. The ground floor was originally a basement, with 3 vaulted chambers which would have been accessed from the first floor. See if you can spot the corbel of a bartizan (turret) which survives on the outer wall, with a human face carved onto it.
The original Dún Formna was restored a few times throughout its history. It belongs to the same era as the more famous Dún Aonghasa on Inis Mór and probably contained some clochán’s of which no traces remain today.