Saint-Caprais Cathedral in Agen features several architectural peculiarities: its Romanesque apse is extended by a single-nave Gothic nave. Replacing an earlier wooden campanile, the current bell tower was built in 1835 at the initiative of Bishop Jean-Aimé de Levezou de Vezins and is unusual in that it consists of three Gothic stylistic elements (lancet Gothic, radiant Gothic, and flamboyant Gothic) curiously presented in reverse chronological order.
A corbel composed according to this principle can still be seen in a corner of the north transept of Agen Cathedral. This corbel, in itself, is a small monument containing two large formerets and a long-span pointed arch.
The paintings on the walls and ceilings depict the history of the arrival of Christianity in the region. A central role is given to the first martyrs of Agen. Other paintings are presented in series: the Evangelists, the Apostles, the patriarchs of the Jewish people (Abraham, Noah, etc.), the great kings of Israel, etc.
The cathedral is much shorter than one might expect, judging by the size of the choir; indeed, political and financial difficulties greatly influenced the cathedral's final form.
The painted decoration was entrusted to Jean-Louis Bézard, a painter from Toulouse who won the Prix de Rome in 1829. He completed the decoration of the chapel of the Hospice Saint-Jacques d'Agen, now the departmental hotel, in 1845, which has since disappeared. At the same time, he began painting the Chapel of the Virgin Mary in the cathedral. He continued decorating the cathedral until 1869.
The choice of themes was made by the cathedral clergy and was the subject of debate between the painter and Abbé Deyche. For the decoration of the apse, the choice was made to depict the martyrdom of the saints of Agen. For the rest of the decoration, the paintings blend local themes and Marian iconography, the great figures of the Bible, the Old Testament, and the New Testament. Jean-Louis Bézard drew inspiration from the decoration of the Sicilian churches of Palermo and Montereale for the medallions of the arches of the transept crossing.
The altar decoration: an altar cross and six candlesticks are listed as historical monuments. On the counter-façade, two statues: on the right, Saint Caprais, and on the left, Saint Stephen, by Louis Rochet.
The main organ, built by organ builder Jean-Baptiste Stoltz, was featured at the 1855 World's Fair in Paris. According to legend, it was donated by Empress Eugenie in 1858 to Agen Cathedral, which until then had no instrument. It is the largest instrument in the Lot-et-Garonne department, with 45 stops spread over three manuals and a pedalboard. It has mechanical action. It is listed as a historic monument.
The choir organ was built by organ builder Jules Magen in 1885 (15 stops over two manuals/pedalboard). It has been listed as a historic monument.
Concert pianist and organist Jérôme Chabert has been its organist since 2002. He founded the Heures d'Orgue, an international festival held every summer in July and August on the cathedral's two organs.