Located in the Île-de-France region, this 36-ton historic mill can rotate on its own axis to track the wind.

A 36-ton building capable of turning to face the wind? It’s not a modern mechanical curiosity, but a mill built more than 250 years ago. Perched on Mont Trouillet in Sannois, Val-d’Oise, the Moulin de Sannois stands as one of the most striking witnesses to the rural past of the Paris region. And contrary to what you might think, it’s not only its sails that can move.

Everything about it comes down to its design. The Moulin de Sannois belongs to the family of pivot mills, also known as chandelier mills. Here, there is no fixed tower topped with a mobile roof: the wooden cage that forms the body of the mill rests on a huge central pivot. The miller could thus rotate the entire structure to place the sails facing the wind. Once the right position was found, the mill would, of course, stay in place while its sails drove the mechanism.

And the dimensions give a sense of the feat: the body of the mill and its pedestal weigh 36 tonnes, the central beam stands six metres tall, and the sails reach roughly 22 metres in wingspan. The City of Sannois today presents the structure as the largest post mill in Île-de-France by size.

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The history of the current mill dates back to 1759-1760. It was built by François Roger, a winegrower from Franconville, on a hill that was especially well exposed to the wind, rising to 162 meters. At the time, the landscape looked very different: as many as three mills had occupied the summit of Mont Trouillet.

The rise of the railway and the era of large industrial flour mills eventually curtailed this activity in the 19th century. Yet the mill survived. The City of Sannois acquired it in 1938, and several restorations have preserved its structure and mechanisms. Damaged by the 1999 storm, it was even dismantled and then restored by specialists in 2007.

Listed on the supplementary inventory of Historic Monuments since 1975, the Moulin de Sannois is now open to visitors at certain times of the year. Inside, gears, millstones, and cogs reveal how a few great sails and a pinch of ingenuity once turned wind into flour.

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