Built between 1906 and 1910, the rotunda of Chambéry is by its dimensions (108 m diameter) the largest rotunda ever built in France, and the only one to remain completely closed today because of its metal framework covering the 360 ° building as well as its central dome.
This monument has been registered for historic monuments since 28 December 1984 and has been labeled "Heritage of the 20th century" since 2005.
It is the largest rotunda ever built in France: its diameter of 110 meters and its 9,500 m2 allow it to accommodate 36 lanes and up to 72 locomotives.
Due to the swamps on which Chambéry is situated, its foundations, like most of the other buildings in the city, rest on piles of wood over a height of 8 meters. They support 5.6 m of ordinary masonry height and 3.45 m of concrete. It is surmounted by a metal frame articulated at its base.
This rotunda, made of iron and metal, was assembled using the technique of Gustave Eiffel by the Magnard workshops of Fourchambault in Nièvre. The work of the 2000s proved to be all the more necessary as the rotunda began to seriously take water during the rain episodes, thus deteriorating the rolling stock parked underneath.
It is now one of the few rotundas in France to be completely closed at 360 ° and still has its central dome (the rotunda type P of Avignon, built in 1946 in concrete and prototype of the series, is also circular on 360 °, but does not have a central dome).