Once elected pope (1644), Innocent X quickly made plans to expand the family complex around the southern part of Piazza Navona. He incorporated older buildings into a newly constructed palace worthy of his recently elevated social status and rivaling those of an older papal family, the Barberini, on the Quirinal Hill. The architect Girolamo Rainaldi and, later, his son, Carlo, constructed the stately and serene, Baroque Palazzo Pamphilj around 1650. They applied the Bernini design to which Francesco Borromini contributed: the gallery connecting the two facades on Piazza Navona, and the Serlian (Palladian) windows (large arched window with two window panels on each side) on the front and adjacent to the church, evoking the image of a papal benediction loggia.
The Brazilian Embassy to Italy has owned palace since its acquisition in 1962.
On the side of the church opposite the piazza, a part of the original Pamphylj complex remains, the Collegio Innocenziano, a seminary founded in 1658 by Olympia Maidalchini. She established it to house and educate young students pursuing priestly ordination. In 1962, at the beginning of the Second Vatican Council, the Pamphylj family (Princess Orietta) made the palace available to the Church for use in their ecumenical endeavors. Since 1969 this building has housed the Centro Pro Unione. Inspired by the ideals of the Second Vatican Council and under the leadership of the Franciscan Friars of the Atonement, the center actively promotes ecumenical dialogue, research opportunities and interaction among diverse Christian and non-Christian religions and traditions. The Centro also houses a library for research and sponsors conferences to promote theological dialogue for its members and guests.
