Not exactly sure who BUILT it but here's some info!
The Rock of Cashel, known in Irish as ‘Carraig Phádraig’, used to be the seat of the Kings of Munster for several centuries prior to the Norman invasion of Ireland, which, at the round of the 12th century, Muirchertach Ua Briain, the then ruling King of Munster, decided to donate his fortress located on the Rock to the Church.
Not sure if it helps but I hope it does!
