3 April. City museums free to Rome residents.
Rome’s civic museums are open free of charge to Rome residents on the first Sunday of every month, with the next edition of Domenica al Museo taking place on 3 April.
Note that the Toulouse Lautrec exhibition at the Ara Pacis and the Renzo Arbore show at MACRO are not included in the free entry.
For full details see Musei in Comune website while for list of museums in the capital see the Yellow Pages section of the Wanted in Rome website.