Exterior view

In 1644, Cardinal Giambattista Pamphilj of the powerful Pamphilj family, who already owned a palace between the Piazza Navona and the Via Pasquino, became Pope Innocent X. With this election came the desire for a larger more magnificent building to reflect his family's increased prestige. Further land was bought, the architect Girolamo Rainaldi received the commission and construction began in 1646. The new project was to incorporate some existing buildings, including the former palace of the Pamphilj and the Palazzo Cibo. The resulting palace is a huge building in which the upper storeys of the central five bays are articulated with tiers of pilasters in a cumulative manner that lends no emphasis to the piano nobile.

The palace's expansive, concave façade was appropriate to both the longitudinal sprawl of the Piazza Navona and the grandeur of the times. The exterior is distinguished by its flanking bell-towers and dome, which form a compositional unit; the dome has a lantern and is placed on a tall drum, the paired pilasters of which link the main portal, with its twin half-columns, to the paired ribs in the dome.

In 1647, Francesco Borromini was consulted about the design and he made a series of new proposals for the palace. However, the prevailing preference was for Rainaldi's more staid and conservative design. Borromini's limited contributions included the stucco decoration of the salone (the main room) and design of the Gallery, located at first floor level between the rest of the palace and the church of Sant'Agnese next door. The Gallery extends through the width of the block with a large Serliana window at either end. The ceiling of the Gallery was decorated with frescoes by Pietro da Cortona depicting scenes related to the story of Aeneas.

The photo shows the façade of Palazzo Pamphilj.