The creation in 1966 of the Museum of Spanish Abstract Art in Cuenca’s Hanging Houses was the fruit of Fernando Zóbel’s pioneering spirit, and also the start of an inspiring chapter of Spain’s cultural history. One of a kind in content and container, it soon became famous internationally. Alfred H. Barr Jr., the MoMA’s first director, called it “the most beautiful small museum in the world.” Now, with air-conditioning works ongoing at the museum, the Juan March Foundation (its manager since 1981) has organized a traveling exhibition of its collections, and the exquisite catalog takes stock of the historical and social vicissitudes of the already classic institution.