They look striking from the outside, it’s true. But the reason many of the nation’s Beaux-Arts landmarks, including Grand Central Terminal and Carnegie Hall, are so beloved is the tile and mortar work of Rafael Guastavino Sr. The Spanish builder and contemporary of Gaudí had his first major U.S. commission with the Boston Public Library. Since their completion in 1890, the Catalan vaults of Guastavino’s ceilings are just as important a part of the library’s aesthetics as its famed John Singer Sargent murals. New York’s City Hall subway station, closed to the public since 1945 and rediscovered every few years by urban spelunkers and Web slideshows, boasts Guastavino’s tile vaulting. And his tile-arch signature can be found in D.C. in the U.S. Supreme Court and the National Museum of Natural History. The National Building Museum, then, is a fitting stop for “Palaces for the People,” a survey of Guastavino’s work that seeks to illuminate his process in part by presenting a full-scale tiled vault. Guastavino designed places that still make jaws drop; this show seeks to explain how.

The exhibit is on view Mondays–Saturdays 10 a.m. to 5 p.m. and Sundays 11 a.m. to 5 p.m. at the National Building Museum, 401 F St. NW. $8. (202) 272-2448. nbm.org.