Aghadoe Cathedral is situated near the town of Killarney, overlooking the Lakes of Killarney. The cathedral's ruins date predominantly from the 11th and 12th centuries, although the site's origins are believed to extend back to the 7th century. The church may have been the seat of a bishop at Aghadoe. The building was constructed in Romanesque style and was dedicated to the Holy Trinity. A carved stone fragment found on the site indicates that Aghadoe Cathedral was still used as a religious site during the 17th century. By 1740, it was no longer listed as an active parish .