This is the 13C Paradise Chapel which is at the heart of St Méen Abbey. The chapel is famous for its remarkable and well preserved 14C frescos which recount the life of St Méven who founded the abbey in the 6C. One of the scenes shows a man playing a violin while a woman dances to the air - this is said to represent paradise, hence the name of the chapel.
@peadar Thanks Peter; the Saint in question is variously named as St. Méven, St. Méwen or the shortened version, St. Méen... he is very much a Breton saint! To get accents on your 'phone, hold your finger on the letter and it will offer you a number of alternatives - just slide your finger to the one that you want and let go.