Behind the building which gives onto the street, there is a small mansion between the courtyard and the garden. It was built between 1776 and 1781 for Madame de Ligniville, Countess de la Baume-Montrevel. It was designed by Claude-Antoine Colombot, one of the greatest Besançon architects of that time. (The house on the street was built in 1753 by his father, Jean-Charles Colombot.)
The facades of this two-storey mansion are decorated in the “Greek” Neoclassical style, with continuous friezes using the Vitruvian wave pattern, and garlands held in place by nails. The interior decorations were in the same style, also designed by Colombot with a team of craftsmen. The stone staircase of honour still exists with its dome and the wrought iron railing.