When the current art museum was home to the hospice for the poor and the sick, this oratory was the church.
The right side of this oratory deserves particular attention and in particular the traces of the ancient Romanesque structure brought to light by the restorations: a small entrance door walled up and surmounted by a lunette, hanging arches decorated with heads of cows and goats, two threaded single-lancet windows that lighten the compactness of the masonry.
The interior has neoclassical ornaments and, on the back wall, stucco statues of the second half of the eighteenth century depicting with beautiful fidelity the Blessed Angelo Porro and San Filippo Benizzi, wearing the austere black habit of the Servites.
The baroque altar encloses a lunette from around 1350: in the centre is the Madonna and Child, flanked on the right by Saint John the Baptist and on the left by a saint identified as Saint Catherine of Alexandria. The fresco has been admired by more than one scholar. Giuseppe Martinola underlined "the vivacity of the colour, the refinement of the hands, the content of the Child's naturalism"; Carla Travi praised "the particular technique of thin and dense hatching with which the freshness gives volume and luminosity to the figures"; Piero Bianconi liked Saint Catherine, who "raises with lively fervor the youthful and full face, delicately painted in pink and framed with blond and thick hair".
As for the author, in 1971 Michele Boskovits assigned the work to Giovanni da Milano, an attribution that critics have shared since then. The artist, a great pupil of Giotto's, painted among other things the frescoes with the stories of the Virgin preserved in the Florentine Church of Santa Croce.