The Church of St. Similien is an ancient church in Nantes. After the death of Bishop Similien in 310 AD, his successor, Eumilius, erected over his grave a votive chapel. One hundred years later, the bishop Leo, a Greek (444-458) built a real church to the site. In 848 AD, Nantes was vandalized during the Norman invasions. In 958 the restoration of the building began and was completed towards 1172 by the Duke Geoffroy II.
Following the siege of Nantes by Louis XI in 1487, Bishop Peter of Chaffault, repaired and enlarged the basilica Building it in the form of a Latin cross. The apse is Merovingian but the nave was extended towards the west, and flanked by two crosses.
During the French revolution, the church was closed to worship in 1793 and reopened after the Concordat of 1802. In 1824, the Millennium old building was destroyed and a church with three naves replaced it. The façade and portico were completed in 1835.
Fifteen years later, in 1850, the parish priest and the Church Council were considering the construction of a new church. In 1869, an architect, Eugene Boismen was appointed. The plans he offers were a Gothic building, inspired by those of the first half of the thirteenth century. The north-west facing building will include three naves, two ambulatory, bedside with a chapel which will be placed Our Lady of Mercy. The nave of five bays and end with a facade with two arrows. Permission to build the new church in 1872 is given. The Bishop Félix Fournier blessed the first stone of the new sanctuary on 5 October 1873. The work was completed in 1894 but as early as 1880, the vaults of the apse, the choir and transept were completed.
References:Saint-Georges de Boscherville Abbey is a former Benedictine abbey. It was founded in about 1113 by Guillaume de Tancarville on the site of an earlier establishment of secular canons and settled by monks from the Abbey of Saint-Evroul. The abbey church made of Caumont stone was erected from 1113 to 1140. The Norman builders aimed to have very well-lit naves and they did this by means of tall, large windows, initially made possible by a wooden ceiling, which prevented uplift, although this was replaced by a Gothic vault in the 13th century. The chapter room was built after the abbey church and dates from the last quarter of the 12th century.
The arrival of the Maurist monks in 1659, after the disasters of the Wars of Religion, helped to get the abbey back on a firmer spiritual, architectural and economic footing. They erected a large monastic building one wing of which fitted tightly around the chapter house (which was otherwise left as it was).