Like in St. Sauvant, 10kms south, Saint-Vivien was erected within the 12th century and got strongly fortified the 100 Years War. At that time the walls of the nave got enlarged - and towers and battlements were added tp the Romanesque church. I was very surprised to find a narrow entrance to a small crypt.
I squeezed through - and found that the crypt was used as an ossuary.