In the 10th century, a community of monks must have lived in Demptézieu, if only for the construction of a church. This monastery, under the dependence of the church of Lyon, managed the town, its lands and its vineyards.
Around 1172, this church was placed under the patronage of Saint Chef and until 1801, it was patronized by the diocese of Vienna.
In the 11th century, the castle of Demptézieu was defended by 15 towers connected by a surrounding wall 800m long and 1.30m thick. These fortifications went as far as the Chapelle Seigneuriale (the current church).
In 1462, the chapel was reported as a parish church.
Over the ages, the Church of Demptézieu was built in 3 stages and underwent numerous transformations.
A plan from 1728 shows a Church in the shape of a cross:
To the right of the choir, the Sainte Madeleine chapel.
To the left of the choir, the Saint Etienne chapel
The bell tower was located in the center of the choir.
In 1885, the church was too small. The chapels were extended into 2 side naves, which transformed the Latin cross into a church with 3 naves.
Today :
To the right of the choir, a chapel dedicated to the Virgin
To the left of the choir, a chapel dedicated to Saint Barhélémy, patron of the parish.
We notice the presence of the bell tower above the porch.
In the choir, a painting of St Barthélémy was offered by the Carthusians.