The Séré family was one of the most influencial families in the city, giving it three mayors during the second XIXth century. Bernard-Louis Calouin de Tréville, father of Henri Calouin de Tréville, was an important figure of the city and its country. After he received the honours for his military career, he made meticulous researches about the contribution of the country of Ariège to any war that France got involved in, effectively becoming a specialist of the military history of Foix.
Atypical residence by its history, the oustal is also so by its building. Its foundations were set in the Middle Ages and the garden wall, on the castle side, was with little doubt a military wall set to defend the county from invaders by creating an extremely narrow passage to the castle. The Patio, which recently got entirely renovated, seems to have been some sort of military building, linked by footbridges to the defense walls of Foix. Its base foundations lets think that the bottom of the building served as barracks.
You can get more information, in the right section, about the two cottages available for rent.