The Palazzo was built sometime between 1471 and 1484 for Cardinal Raffaele Riario, the nephew of Pope Sixtus IV who reigned during that period, but, unlike many other Roman Palazzi built by papal nephews, it was not build with church funds. The good Cardinal built his house with 60,000 scudi won in a single night of gambling from another important nephew, Cardinal, Francheschetto Cibo, whose uncle was to succeed Sixtus IV and become Pope Innocent VIII. Trying to determine how much that might be in modern money is difficult, but it must have been a lot from the looks of the palace it bought. Romans of the time were familiar with the custom of building palaces for Cardinals using church funds, but, judging from the fact that it became part of Roman lore, they must have been at least a little scandalized by how Cardinal Riario got the money for this one -- at least by the size of the stakes the Cardinals' card game.
Nobody knows for certain who designed the Palazzo, because the records appear to have been lost in the sack of Rome in 1527, but there are theories: architectural historians say there are distinct Florentine influences. Giorgio Vasari, an artist and art historian of the next century, said that Donato Bramante was the architect, but that was clearly impossible because Bramante was not yet in Rome when the Cancelleria was built. Bramante may later have done the grand multi-level pillared courtyard, but even that is occasionally disputed. The main door and the balcony above it are by Domenico Fontana and were added during the reign of Pope Sixtus V. The rest of the Palace is now generally attributed, based on design and artistic affinities, to Andrea Bregno and/or Antonio da Montecavallo.
The only decorations on the outside of the palace, aside from window and doorway treatments reminiscent of ancient Roman styles, are some examples of the Riario heraldic roses, the dedicatory inscription running the length of the front, and papal arms at the corners (added later.)
The architectural gem of the interior of the palazzo is the "Bramante" courtyard which has three levels of porticoes adorned with 44 fine granite columns which are thought to have been taken from Pompey's hekatostylon, the "hundred-pillared" ambulatory next to his theater, and with more Riario roses. This courtyard for years was only available for an occasional quick peak through the door when it might be opened briefly to allow in a Vatican limo. Now you can walk right in on the ground level, and a stairway on the left takes you up to the piano nobile level of the portico, which is also open.
The interior decorations of the viewable part of the palazzo have never attracted the same level of critical praise as its architecture. It is probably, therefore, just as well that the newly installed lighting in the very large Sala Riaria (the main reception room, which is profusely frescoed by unidentified Renaissance artists) is designed to emphasize the exhibition of ancient biblical manuscripts that occupies this hall and the adjoining Sala dei Cento Giorni. The Sala dei Cento Giorni is so named, because Vasari, after installing its frescoes in the next century, boasted to Michelangelo that he and two students had finished the whole room in one hundred days. Michelangelo's famous retort was supposedly, "It looks like it." Both rooms have been extensively and very meticulously restored adopting the modern convention of clearly delineating original and restored sections.
The "Codex B" biblical exhibition in the two rooms is superb. The many manuscripts and a few later typescripts are all from the vast Vatican Library collections. They are mounted in antique, glass-covered, wooden display cases, each piece is labeled in Italian and English, there is good explanatory signage for the various sections, and the lighting is very good and accurately aimed at the documents. The real "Codex B", one of the oldest, most valuable, and important ancient biblical manuscripts anywhere, is on display, along with numerous other ancient bibles and fragments. Like the rooms they occupy, most of these documents have never before been publicly displayed. (Although the early bibles might be available for study by selected scholars, getting a "Bibiae" endorsement on your Vatican Library card is not easy!) "Audio guides" are available in English and Italian. A lavish exhibition catalog is available for IL 100,000. The entry fee is IL 12,000.
The second exhibition in the palace, "Saints Peter and Paul, the History, the Cult, the Memories of the First Centuries" occupies recently renovated basement rooms. The exhibit space is composed of a series of stark white vaulted rooms, indirectly lit and climate controlled. Several rooms have glass floor sections through which you can view portions of the ancient structures below, parts of the earlier iteration of the Church of S. Lorenzo in Damaso. One of the larger rooms has a balcony overlooking a glass-covered part of the S. Lorenzo excavations. That church was demolished, and a newer, grander church of S. Lorenzo was constructed within the Cardinal's palazzo but with a different orientation.
The exhibition is in five sections: (1.) "The Origins of Christian Rome" -- where the Christians came from, how they arrived, and how they fit into the pre-existing Jewish community, (2.) "The Spiritual Climate of Late Imperial Rome" -- Roman and "mystery" religions, (3.) "Peter and Paul, the Story" -- their personal histories and how they came to be in Rome, (4.) "Peter and Paul, the Invention of Images" -- representations and iconography, and (5.) "Remembering the Stories, the Genesis of the Theophanies" -- how their stories were disseminated and the reactions of later Christians. Each section is illustrated by appropriate art in the form of sculpture, medals and coins, utensils, and other artifacts drawn from museum collections in Italy and abroad. A very good "audio-guide", which explains the significance of every item in the exhibit, is available, but only in Italian. The exhibition catalog, also very good, costs IL 95,000. Entry fee is IL 14,000, but you get a reduction if you show the ticket from the other exhibit.
Both of these exhibits are highly specialized, and they have an avowedly Roman Catholic bias, but they are worth the visit both on their own merits and as a way to get into the Cancelleria. Neither of the exhibits would have much appeal for kids.
P.S. -- At the top of the stairway to the piano nobile of the Cancelleria is a doorway marked "Penitentiary". There are no prisoners inside and never have been. The Papal Penitentiary is on of the three Papal Judiciary offices in the building and it is concerned with penitence and "indulgences," which you might know about from Christian church history. The other two offices are the Apostolic Rota, an ecclesiastical court, and the Signatura, which prepares, verifies, notarizes, and archives documents with Papal Signatures.
http://www.geocities.com/Paris/LeftBank/7798/Vasi/Vasi74.html captioned pictures
http://www.tulane.edu/lester/text/Renaissance/Italian.Renaissance/Italian.Renaissance45.html Small site with a really good outside picture
http://www.siba.fi/~kkoskim/rooma/pages/PCANCELL.HTM Drawing and pictures, including two of the courtyard
http://18.104.22.168/welcomeitaly/roma/artecultura/palazzi/palcancelleriaing.html Short description
http://www.boglewood.com/cornaro/xvasari.html Vasari Bio