The plan of the church is composed of a central nave with aisles according to a frequent plan in Romanesque architecture of Poitou. The interior has the effect of a "church agora" on just one plane. The barrel vault has a slightly flattened silhouette, whereas the aisles are covered with a groined vault. Outside, the aisles were covered with a terrace punt[clarification needed], the roof being reserved for the nave: thus there was the effect of a basilica on two levels. This silhouette disappeared with the Gothic remodelling. A deambulatory with radiating chapels developed around the church which preserved a part of its murals. A crypt of the 11th century, dug a posteriori under the choir, also preserves frescos of the time. The plan does not have transepts, for good reasons: buildings were in the north, and the principal street passes to the south. The Romanesque gate is preserved in part to the south. Cut down by this stage, one found there before the Revolution, an equestrian statue representing Constantine. This statue was the counterpart of another, older statue destroyed by the Huguenots in 1562. It is not known if the identity of the first rider had been the same. Behind this statue, on the ground, a small vault dedicated to Saint Katherine was referred to during the Middle Ages. The bell-tower dates from the 11th century. In the beginning it was much more obvious: the first level is concealed today by the roofs. Located at the site of the crossing, it presents a square base, then over it a circular level of a roof decorated with tiles. This type of roof, frequent in the south-west, was often copied by the architects of the 19th century, in particular Paul Abadie in Angoulême, Périgueux and Bordeaux.