The ground plan of the building is irregular in order to fully occupy its street corner location. At first glance it appears to be rectangular, but closer inspection reveals that it is in fact an irregular
pentagon. The palace comprises five floors above a semi-basement. Its style is broadly based on
Palazzo Farnese; the lower floors exemplifying the architecture of the late Renaissance found in Rome and throughout
Lazio. The principal façade comprises five bays. The ground floor is pierced centrally by the entrance to a
porte-cochère leading to an internal courtyard. The corners of the irregular building are accentuated by
quoining, while shallow
pilasters divide the five bays from the first floor upwards. Externally, the ground floor shows banded
rustication (very similar to that found in the Roman
Palazzo Vidoni Caffarelli, built in 1515 and attributed to Raphael), while the floors above are of rendered ochre
ashlar. In the custom of the time, the ground floor was designed for occupation by only horses, servants and domestic offices. Here on the first floor, the
piano nobile, were the principal rooms. As in most Renaissance palazzi, the upper floors are reached by a broad stone staircase rising from the cloisterlike inner courtyard, this negated the need for the upper floor's noble occupants to ever visit the menial ground floor rooms. The piano nobile contains an
enfilade of principal reception rooms; the importance of these rooms is denoted on the exterior by the large size of the windows and their alternating segmental and pointed
pediments. of the Piazza Nicosia in 1748. The obtuse corner of the building (‘’pictured below’’), with its fountain, is to the left. The second floor is aesthetically divided from the first by a double band and it is quite possible that all above this band is a later addition. If this were the case, then the palace would have originally followed the simple two-storey design, which so appealed to Raphael. The early architectural history of the building is poorly documented. What is known is that in 1701, architect
Carlo Francesco Bizzaccheri added the top floor. However, the architect was either not working in his usual style or it has been subsequently altered, for the uppermost floor appears of no more architectural merit than those added to many other palazzi during the eighteenth and nineteenth centuries. It may be that Bizzaccheri's work was altered; circa 1746 the building was acquired by the newly ennobled Negroni family who sometime between acquiring ownership and 1759 modernised the principal façade, creating its present-day appearance. This work included the Baroque pediments of the second floor windows and the pediments of the mezzanine floor. The latter were decorated with sheaths and arrows from the Negroni coat of arms, while the central pediment of the piano nobile was given extra prominence by the addition of a Negro's head in bas relief, the armorial crest of the Negroni. and it was probably replacing an existing fountain during the Galitzin era of the later nineteenth century. The second fountain is on the external corner of the palace which tapers to the confluence of via dells Scrofa and piazza Nicosia. This is a more simple utilitarian tough fountain for the use of animals and people on the street. The ready supply of water to the building came from the re-opened the
Acqua Vergine aqueduct, which had been restored in 1453. == Occupancy ==