The first world exposition, held in London in 1851, occupied Joseph Paxton's Crystal Palace. But during the last century, expos (also called world's fairs) evolved into collections of national pavilions that competed for attention with novel and grandiose building designs. The Shanghai Expo in 2010 kicked off the “Asian century” with a show of architectural pyrotechnics that reportedly attracted 73 million visitors.

The theme of Expo 2015 in Milan is “feeding the planet: energy for life.” Initially, a master plan by architects Jacques Herzog, Mark Rylander, Ricky Burdett, Stefano Boeri, and William McDonough proposed that each participating country get a “standardized” pavilion, giving them a chance to distinguish themselves with content, not starchitecture. But Expo organizers succumbed to political pressure, and the fair devolved into another architectural bake-off, particularly jarring because the site is relatively small at 490 acres (compared to Shanghai's 1,300 acres). This creates unfortunate adjacencies. The impressive Chinese pavilion designed by Yichen Lu, for example, looks almost ridiculous flanked by a “Zen Express Street Food Corner” and a gaudy Swatch kiosk. Every few hundred yards, there's a large, motel-like building housing restrooms, cafés, and other essentials. Otherwise, the expo is a free-for-all. The problem with abandoning the original master plan isn't that the architecture got wild and woolly, but that the theme—which promised discussion of a vitally important subject, and an opportunity to compare apples to apples—disappeared along with architectural restraint.