It is an open secret among residents of Barcelona that one of the greatest art treasures in the city is housed at the National Museum of Art of Catalunya. While many of the collections of paintings and sculptures are mediocre, the magical, mystical installation of medieval frescoes is unparalleled. Most of these treasures were discovered at the beginning of the 20th century in crumbling ancient churches in the Pyrenees. When one such church was sold to Boston’s Museum of Fine Arts, it set off a storm of outrage over losing Catalunya’s cultural patrimony, leading to church after church being purchased by public institutions. Skilled conservation teams then detached fragile and fading mural paintings from the walls and ultimately moved them to this museum. MNAC displays more than a hundred pieces from the churches, accompanied by contemporaneous panel paintings and polychrome wood carvings, most of them dating from the 11th to 13th centuries, a fundamental period in Catalan art. Elsewhere in the vast museum building (originally built for the 1929 Barcelona International Exposition), lower level galleries are devoted to a wide range of popular traveling exhibitions; a Modernista section displays treasures like a 1907 fireplace by Domènech i Montaner and paintings by second-generation Modernista artist Joaquim Mir, as well as works by Catalunya’s only noted Impressionist painter, Marià Pidelaserra. The museum interior was given a facelift for the 1992 Olympics, based on plans by architects Gae Aulenti and Enric Steegmann. Take a break from the galleries and go up to the roof for a spectacular view.