Great news: Across Europe, museums will be free and open late the night of May 14.
A little more unusually, it also includes museums not often part of these free events, like the Scuderie del Quirinale (currently with a Lorenzo Lotto exhibit); the MAXXI, with its great Michelangelo Pistoletto exhibit; and the Palazzo delle Esposizioni, with its show on European 19th- and 20th-century art including pieces by Corot, Monet, Renoir, Ernst, Klee, and Picasso.
All will be open, and free, from 8pm-2am, with last entrance at 1am.
Another bonus? The Palazzo dell Esposizione hosts two piano concerts by Michelangelo Carbonara, one at 9pm and one at 10:30pm, celebrating the same time period that's also shown with the exhibit.
Happy free culture!