Mont Thou, Mountain summit in Metropolis of Lyon, France

Mont Thou is a mountain in the Metropolis of Lyon that rises to 611 meters and provides views across the city and surrounding countryside. Several walking trails lead up from different directions, making it accessible from various starting points.

The summit's military role began in 1970 with the installation of a Palmier radar: a 15-tonne, 100 m² three-dimensional set turning six times a minute, operating around the clock to track aircraft altitude, distance and bearing within 400 km for the air force base at Mont Verdun. In May 2018 it was replaced by a Ground Master 406 radar, and the radome was dismantled in 2024.

The mountain appears in Lyon's dialect literature: Jacques-Melchior Villefranche's Essai de Grammaire du patois lyonnais rhymes Mont Cindre, Mont Thou and Mont Verdun as "three giants that are but one, straining to see Lyon". The summit holds an orientation table, and the radar dome and Orange relay mast stand beside it.

The summit is reached on foot; the orientation table there helps identify Lyon, the Rhône plain and the Alps. The military radome and the Orange relay mast stand beside it, so the top is a working telecommunications and air-control site rather than open parkland. The radar was replaced in 2018 and the radome dismantled in 2024.

At the summit stood a military "Palmier" radar dome built in 1970: 15 tonnes, 100 m², six rotations per minute, tracking aircraft within 400 km for the Lyon-Mont Verdun air base. A Ground Master 406 replaced it in May 2018, and the dome was dismantled in 2024. An Orange 2G/3G/4G mast stands beside it.