The section of the underground gallery accidentally discovered in 1978 poses three problems : extent, function and date. It seems to belong to a much larger whole distributed about the chateau in three directions : north, south and east. Among the plausible hypothèses concerning its use, only one can be considered for the moment, the idea of a défensive function within the f rame work of médiéval fortifications. Comparison of this construction with tradi- tional local buildings allows only a very wide dating, between the 13 th. and the 17 th. centuries. Historical documents enable us to specify that an underground defence would no longer hâve had much point after the destruction ofthe ramparts in 1573. A more thorough study of ail the loca...