In the 15th century, this town was called Mirambel l'Artaud or Artault, a name borne by its lords from the 11th century to the 13th century. Froissart designates it under the name of Mirabel. An act of June 1645 designates this parish under the name of St Sébastien-les-Mirambeaux. This populous town, which had become the capital of the canton, presented the singular exception that, for the spiritual, it depended on Petit-Niort, whose church had become the parish center of the two localities. This state of affairs dates back to the beginning of the 17th century, when the church of St Martin was called upon to replace that of St Sebastian, which had just been completely destroyed; it has finally ceased in recent times.
From the 11th century, Mirambeau had a church dedicated to St Sebastian, from Narbonne, martyred in Rome, under Diocletian, in the year 288 of the Christian era, as mentioned in the charter of the abbey of St Savinien, near Lyon, dated from the year 1062. In the 11th, 15th, 16th and 17th centuries, the priory of St-Sébastien de Mirambeau was still at the presentation of the abbot of St-Savinien de Lyon. One sees opposite the gate of the castle, while going up to the district called the City, a stone cross which indicates, one says, the site or was the church of St-Sebastien. In addition, there is between Civrac and the town, on the edge of the chemin d'Allas, the site of a chapel which formerly belonged to a commandery (this is still the name of the neighboring hamlet). - to be the so-called chapel of the Way, in the parish of St-Sébastien, according to the pouillé of 1746, and which was at the presentation of the diocesan bishop.
Assisted by the generosity of the Countess Duchâtel, Mirambeau undertook the construction of a chapel, which was completed at the end of 1856. This building, too cramped, with modern forms, and without religious character, consists of a nave of 33 m long, 9 wide, with semi-circular apse and side chapels. They are dedicated to the Blessed Virgin and to the Sacred Heart.
The chapel on the left was later rebuilt, with painting in the Byzantine style and ossuary, by the Duchâtel family, whose particular burial place it is.
A basket-handle ceiling conceals an elegant framework in the nave. A porch of six steps leads to the main door of the chapel, which is surmounted by a slender quadrangular bell tower, and whose spire is covered with slates. This chapel occupies the very site of the former house of the Récollets de Mirambeau,
We see in the church of Mirambeau, a crucifixion of Our Lady, a recent gift from the government, and an Immaculate Conception of Our Lady, a copy, it is said, of a painting by the famous Spanish painter Murillo. Plus a stone baptismal font, sculpted with art, and coming from the old chapel of the Récollets.
While the title of canton cure was conferred on Mirambeau, Petit-Niort became a desserte, or third class cure, although this small population group does not even today have the title of commune.