Abu Dhabi International Airport, United Arab Emirates (AUH/OMAA)

Designed by the French architecture firm ADPI, this tower at Abu Dhabi International Airport was completed in 2011 after only 629 days of work. At the peak of construction, 1,200 workers were on site 24 hours a day. More than 44 miles of cabling run up the central column, sandwiched between high-speed elevators that ascend to the 20th story in 55 seconds. The east and west facades are covered by ethylene tetrafluoroethylene panels, a transparent polymer material. They allow for interior sunlight during the day and provide a glowing effect at night. (Image by Carolyn Russo, National Air and Space Museum, Smithsonian Institution)

They are towering beacons in the sky, functional fixtures vital to aviation, but travelers rarely give airport traffic control towers a second look. An aims to change that, with photos that focus on the simple, rarely-seen beauty of these towering, architectural wonders, exploring structures in airports around the world.

Smithsonian photographer Carolyn Russo traveled to85 airports in 23 countries to capture images of these towers and presenting them as "monumental abstractions, symbols of cultural expression and testimonies of technological change." For Russo, airport towers do more than handle all takeoff, landing, and ground traffic at airports, they become symbols of their airports—and even their countries.

Visitors to the Stockholm-Arlanda Airport in Sweden, for example, are greeted by two lookout points perched like birds at the top of the control tower to evoke protective ravens from Nordic mythology, while the crescent-shaped tower at the Abu Dhabi International Airport (it is the only tower in the world that takes the form of a crescent) resembles the sail of a dhow boat to emphasize the area’s proud maritime heritage.

(MORE: )

"Airport traffic control towers have a powerful presence—they watch over the vastness of the airport and sky, are a nonjudgmental cultural greeter, a choreographer or conductor of the aircraft dance, a mother bird caring for her flock and an omniscient, intelligent structure keeping humans safe," said Russo. "I saw them as the unsung heroes of the airport landscape and tried to elevate them beyond their height and amazing architecture."

To photograph the towers, which also include structures at Austria's Vienna International Airport, Edinburgh Airport in Scotland, United Kingdom and Ronald Reagan Washington National Airport in Virginia, Russo worked with the Federal Aviation Administration, airport authorities, governments and air traffic control agencies around the world.

The exhibition also includes photos of historic, inactive towers, such as those in New York's La Guardia Airport and Barcelona's El Prat Airport. These towers were captured in their natural state, as witnesses to aviation history.

View the slideshow above to see photos of airport towers around the world, photos that tell the story of changing technology, design and architecture, making the case for the preservation of these unlikely art forms.

The exhibition is open through November 2016. A traveling exhibition tour begins December 2016.