Le Blanc is located on the border of Berry, Poitou and Touraine and could "guard" a ford to cross the Creuse. The river actually divided Le Blanc into a "lower town" (Berry) and an upper town shared between Berry and Poitou.

There were two border-fortresses here. Saint-Cyran in the upper town was erected in the 12th century right next to the Château de Naillac, served as a castle chapel and was included in the fortified enclosure.

The church got remodelled and enlarged in Gothic times.