Château de Montlhéry

A gate tower protected the entrance on the opposite site.

Recent evidence suggests that there may have a second court or bailey extending in front of the present gate, as well as a substantial chapel inside the presumed lower court.

Thanks to its position, the keep was notably connected with the scientific experiments of Pierre Gassendi (measurement of the speed of sound), Claude Chappe (experiments with optical telegraphy in 1794) and Alfred Cornu (measurement of the speed of light in 1874).

Visitors today can see the keep, the well, the moat and the remains of the curtain wall.

It has been listed since 1840 as a monument historique by the French Ministry of Culture.