The plaque above the doorway has the coat of arms of Urban VIII, with Barbarini bees, Papal tiara and keys.

A commission that involved Borromini as an architect of both churches and palazzi was the Collegio di Propaganda Fide, the headquarters of the Catholic missionary congregation. Although he took charge of building work in 1646, his greatest contributions to shaping the palazzo belong to his last creative years. The complex includes a dormitory and chapel as well. The College was founded by Urbanus VIII for the training of missionaries. The palace is still devoted to its original purpose, but the ground floor has been converted to shopping. The facade over the Piazza di Spagna is by Bernini, whereas Borromini designed the convex and concave entrance facade facing Via Propaganda.