This building was originally formed as the south end of the priory and dates back to the 13th Century. The refectory would have been on the first floor and was the dining hall where the monks would have eaten. A kitchen was added at the east end of the building in the 16th Century. The monastery is believed to have been founded by a 6th Century holy man – St Seriol – a friend of St Cybi, whose monastery was further across the Isle of Anglesey in Holyhead.