When it opened in 1997, the Guggenheim Museum Bilbao was instantly embraced as an architectural masterpiece. Frank Gehry’s curvaceous structure in iridescent titanium, a magnificent showcase of contemporary art, began drawing a million visitors a year to Spain’s northern coast.

Bilbao itself, however, was a grimy reflection of its industrial past. The Nervion River, which bisects the port city (and runs beside the Guggenheim), was the most polluted waterway in the country, having served as a toxic dump for the shipbuilding and mining industries that flourished in Bilbao in the 19th century.

But with the demise of its primary industries, Bilbao embraced tourism, and in the process became a textbook example of urban renewal. Today, the Nervion is significantly cleaner, thanks to the absence of sludge-producing factories and the addition of a sewage treatment plant. The city razed its decrepit port and moved it downstream to the Bay of Biscay. And several new architectural features have jazzed up Bilbao’s skyline: a soaring footbridge (that spans the Nervion) designed by Santiago Calatrava, curved-glass metro entrances by Sir Norman Foster, and a striking white airport terminal, also by Calatrava.

Perhaps the greenest element of Bilbao’s makeover is the work of landscape designer Diana Balmori, who transformed the old port area into a riverside park and promenade (below). Her open, grassy design invites pedestrians to walk, sit and bicycle along the previously inaccessible river and enjoy views of the surrounding mountains. The plan also incorporates a light rail system, which glides over generous swaths of lawn as it whisks passengers to the Guggenheim, the opera house and beyond. The lawn is sustained by Bilbao’s misty climate.

Head of New York-based Balmori & Associates, Balmori works to integrate sustainable landscape with urban architecture. In 2006, her firm planted New York City’s largest green roof, atop Silvercup Studios in the borough of Queens. Balmori is currently developing the building plans for an innovative “green city” in South Korea, the country’s new Public Administration Town (below).

Deborah Hay is a New York-based freelance writer specializing in modern art, travel and various environmental issues. Her work appears in Diversion magazine, Wildlife Conservation magazine, and Everett Potter’s Travel Report.