The interior of the church is brigh

The interior of the church is bright, and the dominating colour is white. Sixteen partly engaged columns of the Composite order support the high entablature. Apart from the main altar there are two lateral altars. You could say that the ellipse of the plan is indented at four places creating four irregular spaces. Two of these are small chapels. The French painter Pierre Mignard (1612-1695) has executed the high altar painting St. Carlo Borromeo contemplates the Holy Trinity with Sts. Jean de Matha e Félix de Valois. Above is the symbol of the Trinitarian order, a cross formed by a red vertical and a blue horizontal bar. This symbol is also found on the tabernacle, on the front of the altar and on the Trinitarian habit. The statues in the niches above the doors on the sides of the main altar are of Sts. Jean de Matha (left) and Félix de Valois.