photos: Terrain:Architects and Landscape Architects

Literally offering a breath of fresh air, the Austria Pavilion is actually a lush outdoor forest, giving visitors the opportunity to meander through and enjoy 12 Austrian ecotypes, from ground-level mosses to towering trees soaring 40 feet into the sky. As visitors stroll on a meandering path through the misty woodland, dimensional letters ahead of them spell out the word "Breathe," which, as guests move further inside, eventually becomes "Eat." That subtle word play underscores the notion that "Air is food," tethering the rather abstract idea of clean, breathable air to the Expo 2015 theme of "Feeding the Planet, Energy for Life." With the help of thermodynamic misting nozzles, which accelerate evaporation rates and oxygen production, the luxuriant vegetation inside the pavilion produces its own microclimate, generating nearly 137 pounds of pure oxygen every hour, or enough to sustain 1,800 people. As cool as a hike in the legendary Austrian Alps, the pavilion is also genuinely cooling: With no air-conditioning technology at all, the Brigadoon-like forest pavilion is always 9 degrees cooler than the exterior temperature under the often-sweltering Milan sun.

photos: Nigel Young; Foster + Partners

Based on a massive scan of sand dunes that captured the belly-dancer curves of silicate grains at the mercy of the desert's howling winds, the United Arab Emirates' Pavilion stretches nearly the length of a football field. Its 39-foot-high walls of simulated sand, made of Fiberglas and reinforced concrete braced by a steel frame, shelter guests who make their way on a slight uphill slope past interactive installations on climate change and water scarcity. Nearly 300 feet later, the path winds up toward an auditorium contained within a golden drum whose 49-foot-height makes it seem more like an oversized magic lamp out of "1,001 Nights" than an Expo 2015 pavilion. Inside the cylindrical theater, attendees witness even more magic: an illusion based on a 19th British trick called Pepper's ghost, where a virtual girl leads the audience in a hip-hop song urging them to help her secure a future free from hunger and thirst.