If you are a contemporary art fan or collector, then Rome does have some great venues where you can experience the best:
Museo Carlo Bilotti: This small museum in the 18th Century Orangery of the Villa Borghese, houses the private collection of paintings, sculptures and drawings of Carlo Bilotti, the Italian-American entrepreneur and art collector. You can also see temporary exhibitions throughout the year.
Galleria Nazionale d’Arte Moderna (National Gallery of Modern Art): Located at Viale Delle Belle Arts in the beautiful building where it has been since 1915. It has works from the 19th and 20th centuries. There are also temporary exhibitions in addition to the permanent collection. You will see works by Giacometti, Klimt, Cy Twombly, Jackson Pollock, Van Gogh, Cezanne, Degas and Rodin. They also have a nice restaurant, Caffe dell Arti, overlooking the gardens.
MACRO: MACRO, or the Museum of Contemporary Art of Rome, is well worth the visit. It is located at via Nizza 138. The building has been featured in the Wallpaper* Guide as a great example of contemporary architecture in Rome. There are several galleries, a bookstore and a sleek café and restaurant on site. They also have a second location in the Testacio area south of the Colosseum. Make sure you check the website as this site was closed for setting up a new exhibit and therefore was not open.
MAXXI: In a new museum building designed by Zaha Hadid, the well-known international architect. It is a wonderful building with two distinct areas, MAXXI Arte for contemporary art and MAXXI for contemporary architecture. The architecture component was filled with models of current and past projects. They work together with MOMA in New York in sponsoring a young architects design competition. It is a great space and well worth the visit. There is a café inside and another café and restaurant across the plaza from the museum, MAXXI21.
The Vatican Museum is really a must. I booked my ticket for the Vatican Museum online which helped me get quicker access by avoiding the long lines. I was not aware of the Collection of contemporary art, which was bypassed by most of the people, but I was very impressed by the wonderful pieces by Matisse, Paul Klee, Diego Rivera, Kandinsky, Rufino Tamayo and Jose Clemente Orozco.