By Scott Elder, National Geographic

The Empire State Building’s facelift included its signature lights, now LEDs with millions of color combinations possible. New York is also tackling the energy efficiency of less prominent landmarks, investing nearly $500 million to improve its million-plus buildings—and is the first U.S. city to divest from fossil fuels.
PHOTOGRAPH BY GARY HERSHORN, GETTY IMAGES
Fenway Park, the Eiffel Tower, Empire State, and other storied structures were upgraded for 21st-century energy efficiency.
The world’s iconic buildings achieve celebrated status because their architecture stands the test of time. But what lies beneath those enduring facades?
Design and engineering evolve quickly, and many urban buildings—nearly half the office space in New York City was built before 1945—predate concepts like sustainability, climate change, and even recycling, resulting in waste and inefficiency.
Enter the retrofit. Aging buildings are updated with new windows, lighting, plumbing fixtures, and heating and cooling systems, ultimately saving owners and operators money while they conserve energy.
Buildings consume 73 percent of the electricity in the U.S., and indirectly create 38 percent of carbon dioxide emissions—more than industry or transportation. To win the battle against climate change, cities will need to run on more efficient buildings. (See what makes a “green building.”)
These historic icons blazed a trail for other buildings to follow.