The original core of the palazzo was built in the 15th century by the order of Girolamo Riario, Lord of Imola, nephew of Pope Sixtus IV even if the palace incorporates a series of pre-existing buildings from the Medieval period.
The building was then purchased in 1568 by the Austrian nephew of Pope Pius IV Cardinal Marco Sittico Altemps. The Cardinal established his own residence in the palazzo, which he enlarged and embellished with characteristic elements such as the panoramic belvedere, the frescoed loggia, the frescos are still visible in the rooms on the main floor, the grand hall with its monumental fireplace, the Church of San Aniceto with its sacristy, and the Chapel of San Carlo Borromeo.
The richness of the palace was a symbol of the owner’s power that’s why the Cardinal also moved here his magnificent collection of antiquities and rare books.  Various painting series was also completed in this period.
The Altemps family remained in the palazzo until the mid-19th century when widowhood and love affairs led to the property being inherited by Giulio Hardouin. At the end of the century, the building was sold to the Holy See, which allocated it for use as a seminary by the Pontifical Spanish College. The palazzo was then acquired and restored by the Italian Government and opened to the public in December 1997.
Palazzo Altemps hosts absolute masterpieces of ancient sculpture belonging to roman noble families, the celebrated Pallavicini-Rospigliosi frescoes, the Egyptian collection, the vast archaeological corpus of Van Gorga, an eccentric collector of the early 20th century. These are some of the treasures of this unique museum that you shouldn’t miss when visiting Rome.

Palazzo Altemps is now one of the sites of the National Roman Museum, specifically dedicated to the history of art collecting.