Situated on the furthermost bounds of the county of Toulouse and the Aquitaine, the castle of Castelnau reflects the continuity of a long noble lineage from the Quercy region. It is now the result of many construction programs. Towards 1,100, the first barons of Castelnau had a fort built on the model of "new mansions" (with a main tower), following that of motte castles. From this original stronghold remains the seigniorial dwelling (second half of the 12th century) and the square keep (beginning of the 13th century). Headquarters of a mightier and mightier feudal power, the castle was soon surrounded by a small village. Thanks to skilful marriages, which enriched the family heritage, the castle was constantly enlarged and fortified. Therefore, behind its defensive walls equipped with firing rooms, a wide moat with bulwarks and high curtain walls linked to each other by circular angle towers, the castle turned out to be impregnable. In the 17th century, it was made more attractive by the construction of richly decorated drawing rooms with high windows, porticoes and balustrade balconies. From 1715, after the last member of the Castelnau family died, the castle experienced a long period of damage, which came to an end in 1896, when the Opéra Comique singer Jean Mouliérat purchased it and started to restore it. He managed to gather a great collection of furniture, tapestries and sacred art pieces. The castle was then given to the state by the owner, when he died in 1932.