(Left) Nelson Rockefeller examines a painting at New York's Museum of Modern Art in 1939. (Right) Diego Rivera, seen here in 1933, works on a panel of his mural in the lobby of Rockefeller Center. (Left) Bettmann/CORBIS. (Right) AP hide caption

itoggle caption (Left) Bettmann/CORBIS. (Right) AP

Yakutsk, Russia is the world's coldest city: average winter temperatures hit -30 degrees. It's also the largest city built on permafrost. Amos Chapple hide caption

itoggle caption Amos Chapple

Solar Sunflowers, an art installation, greets visitors to Mueller's commercial and retail hub off of Interstate 35. The panels power a nightly light display and return power to the grid. When the development is complete, five miles of granite trails will connect the residents to its commercial and retail hubs. Julia Robinson for NPR hide caption

itoggle caption Julia Robinson for NPR

Fruit by Nike is a piece by designer Peddy Mergui in his exhibit "Wheat is Wheat is Wheat," next on display in May at Expo Milano 2015. Courtesy of Peddy Mergui hide caption

itoggle caption Courtesy of Peddy Mergui

After designing a soy sauce bottle for Kikkoman in 1961, Kenji Ekuan went on to design everything from motorcycles to a bullet train. Mj-bird/Creative Commons hide caption

itoggle caption Mj-bird/Creative Commons

Artist Jesse Howard filled his 20-acre property with hand-painted signs. Collection of the Kansas City Art Institute. hide caption

itoggle caption Collection of the Kansas City Art Institute.

Afghan war rugs reflect the nation's long history of conflict through one of its most ancient art forms. Courtesy of Kevin Sudeith hide caption

itoggle caption Courtesy of Kevin Sudeith

A resident of Lathrop Homes leaves one of the few occupied buildings in the development. The city wants to redevelop the public housing as mixed use, and offered vouchers to encourage residents to relocate. Cheryl Corley/NPR hide caption

itoggle caption Cheryl Corley/NPR

Icehotel is located 120 miles above the Arctic Circle. The temperature outside is well below zero, but inside the hotel — while still, of course, below freezing — it's much warmer, hovering in the low 20s. Ari Shapiro/NPR hide caption

itoggle caption Ari Shapiro/NPR