The Château de Gérigny, a former stronghold converted into guest rooms, is open to the public all year round. The owners would have discovered the entrance to an underground passage there, but no trace of treasure... Do you have enough flair to smell the existence of the latter?
I always knew it was more or less abandoned before the 2000s but there has been good renovation work, especially on the roofs. The exterior facades deserve a major facelift but not easy with the moats.