Built on a rocky outcrop overlooking the entire region, the garrison enjoyed a strategic defensive position.

During the French Revolution, Gaspard de Montmelas, Blaise's younger brother, was imprisoned in Lyon; a delegation of villagers took the road to deliver him.

There remains of the medieval castle a cylindrical keep which dominates a quadrangular enclosure provided with the angles of watchtowers, as well as a vast fenced poultry yard.

It is situated on the top of the Saint-Bonnet hill, overlooking the whole Rhône and Ain departments, from Mâcon in the North to Lyon in the South, and to the Alps in the East.

An association called "Autour de la chapelle Saint Bonnet" was created in 2019 to raise funds to restore the building that has been crumbling down over the years.