The small square tower nestled in the south west corner of the fortress (number 7 on the plan above) is a remnant of the aerial telegraphy invented at the end of the 18th century by the engineer Claude Chappe (1763-1805), using semaphore signals.
Claude Monet | Claude Debussy | Claude Lorrain | Claude François | Jean-Claude Van Damme | Claude Lévi-Strauss | Claude Royet-Journoud | Claude Chabrol | Jean-Claude Carrière | Claude Vivier | Claude Shannon | Claude Berri | Jean-Claude Colin | Claude Rains | Claude Bowes-Lyon, 13th Earl of Strathmore and Kinghorne | Christo and Jeanne-Claude | Jean-Claude Gérard | Claude Lelouch | Claude Jade | Claude Garamond | Claude Bolling | Claude Auchinleck | Jean-Claude Duvalier | Claude Thornhill | Claude Simon | Claude Nicollier | Claude Mollet | Claude Lecouteux | Claude Joseph Vernet | Claude Dubois |
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).