The visitor who enters the Oratory can notice, around him, an explosion of colors and harmony. In reality, the decorative project was conceived by the painter Giovan Domenico Lombardi (1682-1751), certainly after the death of Bonaventura, who would not have wanted this idea of pomp. Lombardi, having a great culture of sixteenth century painting, especially referring to Titian, Tintoretto and Veronese, decided to propose clear and bright shades, which underline the majesty and enhance the details. The presbytery, framed by a small choir in carved and painted wood, shows a perspective game composed of staggered planes. In the center of the triumphal arch there is a wooden statue painted in imitation of marble and is kept in a niche where the Angel is unveiled by a pair of large angels, illusionistically reproduced by the painter. There is also no lack of cherubs holding a floral festoon and which are partially made of stucco. On the back wall of the oratory there is also the Madonna and Child who appears among the clouds. The typical techniques of the Baroque can be observed in various points of the religious building, for example in the phytomorphic figures (plant intertwining) or in the marble folders with shells and cornucopias.
Along the walls 9 canvases have been placed depicting episodes from biblical history in which the intervention of angels plays an important role. For example, there is the painting with the Last Supper, by an unknown artist. It is surrounded by fake marble folders with figures of angels showing the instruments of the Passion. Above the altar is the nineteenth-century wooden crucifix with golden rays, while on the frontal under the altar table stands the tondo on a table depicting the Guardian Angel.
In 2017 the Cassa di Risparmio di Lucca Foundation, in order to preserve and recover this rare jewel of Baroque art and return it to public use and utility, obtained a free loan from the Diocesan Body, owner of the complex, and therefore launched an intense recovery campaign also thanks to the contribution of Azimut Holding SpA, which directly supported the restoration of seven of the nine canvases present.