This palace was created thanks to Pope Sixtus IV (1471-1484), who while considered by historians a rather poor shepherd of the Church, was a great patron of the arts. His other weakness apart from art was love of his family. His nephew and nepot Girolamo Riario was granted not only titles and apanages but also the possibility to marry into the Milan-based Sforza family. The only place which was fit for the newlyweds in Rome was a city residence, on which the works were begun as soon as Sixtus ascended to the papal throne. However, the couple never settled there, since the works lasted extremely long. Abandoned and left by descendants, it was not finished until 1520 when it was inhabited by the Spanish ambassador, while all of the area around Piazza di Sant’Apollinare became a Spanish enclave. It was at that time that the palace courtyard designed by Baldassare Peruzzi was created. In subsequent years the owners changed, until finally in 1568 – the palace still requiring furnishing and decorations – was purchased by Marco Sittico Altemps –a German cardinal, who before he had Latinized his name was known as Markus Sitticus Hohenems. At that time he was one of the most influential people in Rome – his uncle had previously been a pope (Pius IV), while his cousin was the later saint (Charles Borromeo). The cardinal had the palace enlarged and renovated. He put his ideas into life with the aid of the builder Martino Longhi (the Elder). It is at that time that the eye-catching decorations of the loggia of the piano nobile were created with a painted pergola, which seemed to be an enormous gazebo. Apart from landscape elements its walls are decorated with putti and nymphs. In the niches of the arcades of the ground floor the cardinal ordered Greek sculptures to be placed, while in the middle of the courtyard – a fountain. He also, did not forget to have the coat of arms of his family immortalized in stone multiple times: an ibex standing on its hind legs. The palace arranged in such a way became a veritable treasury of books and a place for the exhibition of an outstanding collection of antique art, a hobby which the cardinal pursued with a passion.

All of his wealth, including the palace was to be inherited by his only son Roberto. However, this did not come about. Sixtus V had become pope in Rome. This fear-inspiring lawgiver announced and introduced severe moral acts, and since Roberto had been convicted of rape and adultery, at the age of 20 he was sentenced to death and beheaded. Despite begging, the father was unable to have mercy granted to his son. After the death of the cardinal, the palace passed on to his grandson, Prince Giovanni Angelo Altemps, who in the first two decades of the XVII century brought even greater splendor to the residence. Within, he created a theatre, where plays and concerts took place, he organized balls, but he also did not forget about the tragedy of his father. He expressed this when in 1605 he was given an exceptional gift by Pope Clement VIII – the very same who had Beatrice Cenci executed and Giordano Bruno burned at the stake. This was an ancient urn with the alleged remains of Anicetus, a pope from the II century, which were discovered under rather mysterious circumstances. Nevertheless, the pope gave it to the prince, who was at that time in the process of furnishing a small private church in one of the parts of his palace. In it, the aforementioned relics were placed. The martyrdom of Pope Anicetus, who – as was claimed (until it was verified in 2001) – was beheaded, brings about references to the death of the prince’s father, giving a double significance to the church as a place of both commemoration and cult. Perhaps Clement VIII, in this way, had wanted to atone for the deed of his predecessor and bring back the good name of the Altemps family, since the recently canonized Charles Borromeo was its close relative.

The Church of St. Anicetus, in which the relics were exhibited was inaccessible from the street and constituted a sort of church chapel. It was the work of well-known and valued architects: Onorio Longhi  and Girolamo Rainaldi, who were employed by Giovanni Angelo. The young prince spared no expenses on its decorations, which included lining from multi-colored marble, mother of pearl and gilded stuccos. The walls frescoes depicting the saint’s martyrdom were completed by Pomarancio (Antonio Circignani).

The further fate of the palace is connected with the highs and lows of the family, constantly plagued by financial problems . As a result the residence was rented out (1725-1732) to the French Cardinal Melchior de Polignac, who also had an influence on its decorations and furnishing. Within its walls theatrical performances and exquisite parties took place, including the banquet to celebrate the wedding of the French King Louis XV with the Polish princess Maria Leszczyńska.

On the other hand, in 1883,  the palace chapel bore witness to the wedding of the last member of the Altemps family, Maria Hardouin di Gallese, with a well-known, but unfortunately unfaithful poet Gabriele D’Annunzio, who quickly abandoned his wife. A few years later the palace was sold to the Holy See to be used as a seminary, which in turn sold it nearly one hundred years later to the Italian state, which organized a museum inside in 1997.

The palace can only be seen as part of visiting the department of Museo Nazionale Romano, which should be specifically recommended, due to an imposing and well-selected collection of works of ancient art. It is an effect of the passion for collection of outstanding Roman families – Mattei, Altemps and Ludovisi.