When the German Pavilion was erected at the 1929 Barcelona International Exhibition, it served one purpose: To “[give] voice to the spirit of a new era.” Designed by architect Ludwig Mies van der Rohe—a man legendary enough to be known simply as “Mies”—and Lilly Reich, the pavilion was built to show the world what the democratically elected and progressively minded postwar Weimar Republic was all about.

The resulting structure has been celebrated as one of Mies’ most daring works. Focused on the concept of free-flowing space, the pavilion featured a fluid interior with slabs of polished marble and glass that acted as walls. A flat roof appeared to float above, supported by slender steel columns. Outside, a large rectangular pool was filled with smooth stones that gleamed ...