Doria Pamphilj: A Plain Facade on Via del Corso

Thousands of people walk past this building every hour and almost none of them look up. The front on Via del Corso is grey, flat and unremarkable, which is exactly what a Roman noble family wanted the street to see. Behind it is one of the largest private art collections still in private hands. The rooms are hung floor to ceiling, frames touching, the way collections were displayed before museums invented the idea of one painting per stretch of wall. It is denser and harder to take in than a modern gallery, and considerably more impressive. Raphael, Tintoretto, Titian, Caravaggio and Velázquez are all on those walls, along with a great deal that would be the centrepiece anywhere else. The Velázquez is the portrait of Innocent X, the Pamphilj pope, and it is worth finding first before the rest of the collection wears your eye out. Skip-the-line entry, and no group: the pace is yours. Seventy minutes is the working estimate, and it is honest rather than generous. The rooms are small, the pictures are three deep on the wall, and the cabinet holding the Velázquez draws a queue of its own because nobody walks straight past it. If you have longer, spend it on one wing properly instead of trying to finish all four. Read the inclusions before booking. The gallery's own audio guide comes with the ticket, along with a second app covering the rest of Rome, which is a different product and will not tell you what is on the wall in front of you. The one conditional item is the Secret Apartments: an option chosen at the time of purchase, not something to request at the desk, and the rooms are otherwise closed. The same upgrade opens Diana's Bath and includes a live classical concert. The Innocent X hangs beside Bernini's marble bust of the same pope, so two portraits of one difficult face stand a step apart. Velázquez painted his in Rome in 1650, and the verdict the family still quotes is the sitter's own: too true. Nearby are the Caravaggios, among them the Rest on the Flight into Egypt, early work and unusually gentle for him, and easy to miss in a room this crowded. The Hall of Mirrors runs along one side, modelled on Versailles and lit from both ends. It is the only space in the building that behaves like the front of a palace rather than a store of pictures. The number to look for on the street is 305. The family still occupies part of the house, which is why the collection has never been broken up and why the hang has never been rearranged to museum taste.