The chapel is the third on the left from the entrance.
It was designed by Guarini but built by his friend Antonio Bettini in 1677. The Teatine fathers composed the songs and liturgy in Latin for the Christmas novena in this church. Today, churches celebrate the novena in Italian, but in memory of the event, the Canons of the College of the Holy Trinity celebrate with due sentiment in the original.
The altar-piece shows the Nativity of the Redeemer and is the work of Pietro Dufour (late 17th century).
The small altar-piece, between the cornucopiae in precious polychrome marble, is particularly interesting because of the three panels in embossed metal: the side ones have coats-of-arms with entwined leaves and flowers, the central one shows the Death of St. Joseph assisted by the Madonna and Jesus – quite a rare image in our churches.
The Nativity is the feast of peace and serenity; over the chapel there are two angels bearing the annunciation:
- one (left) carries a snapped bow;
- the other (right) has a quiver containing splintered arrows: the broken instruments of war!
The stucco decoration on the basin above the altar-piece shows the assumption of the Virgin in a mandorla of flowers and fruit: MAIESTAS DEI.
The confines of the mandorla emphasise the sense of the divine: the Madonna overflows the mandorla and floods everything around like a waterfall. This type of image is quite frequent in medieval art.