There are two churches on this site, portions of which date back to the 15th century.
The first, a roofed church – was originally built during the 12th century, although few of the oldest parts remain visible. It was built in the shape of a cross, but only the center beam survives. The remains contain some striking Romanesque features in the chancel, including an arch that is decorated with ornamental sculptures of heads. The east wall of the chancel once contained an original 13th century window, recently replaced by a modern one. Also during the 13th century, a vault was added, along with a special chamber above the altar.
The nave, added in 1732, sits atop a 15th century foundation and features a window decorated with depictions of a dragon eating its own tail, along with a griffin and bird. In the east gable, there is a beautifully decorated round Romanesque window. Another church stands close by, estimated to date back to the 15th or 16th century. It also appears to have incorporated parts of earlier churches standing on the same spot, including a fine Romanesque doorway and windows.
It also appears to have stones that may have been taken from the roofed church at some point in time.
The site of the churches at Rahan had its beginnings as an ecclesiastical region in 580. Constantine, a Cornish King, retired there from his throne and became a monk. The monastic community was founded by Saint Cartach, a prominent figure in Early Christian Irish history. He was forced into retirement at Lismore, County Waterford, in 636.
The settlement was reestablished in 760 by Fidhairle Ua Sleanaigh and operated until sometime during the twelfth century, after which only the two churches survived.