The former cathedral of Castres dates from the late 17th century, replacing an earlier medieval church that had been damaged in the Wars of Religion. It is a large baroque building, oddly proportioned because the original plans were never completed — the intended western towers were never built, and the facade was simply walled off where they should have been.
The interior is more impressive than the outside suggests. A wide nave with side chapels leads to a domed crossing decorated with a late 17th-century painted ceiling by Brodelet. The choir holds a series of large Baroque altar paintings, several attributed to followers of Mignard. The cathedral lost its status when the diocese was suppressed after the Revolution and is now simply the parish church of Saint-Benoît; it is normally open during the day.