He helped the Mattei rise to prominence by supporting political and cultural initiatives of the Pope and the Church in Rome.
When Pope Paul IV decided to build a wall around the Ghetto in 1555 and imprison the Jewish population, Mattei was given a key to the gate.
[1] In an original plan of 1570 a new fountain was to have been placed near the Theater of Marcellus in the Piazza Giudea, the site of a market in the Jewish ghetto.
The father, suitably impressed, allowed the marriage to go ahead, and Mattei, to remember the event, had the window overlooking the fountain closed up.
On 23 May 1589, Sixtus V issued the following order: Cavalier Domenico Fontana, you will consign to Muzio Mattei or to such other as he shall instruct five pieces of peperino from those brought from Settizonio,[6] which We give to him for use in his fountains at Strada Felice and Strada PiaThough his role is unclear, he was also responsible for some portion of the planning or construction supervision for the Palazzo Albani del Drago on the Quirinal Hill.