The art of the airport tower
During the busy holiday travel season, the last thing many of us think of as we take off or land is the humble airport tower.
Unless, that is, you've seen one of Carolyn Russo's photographs. A photographer at the Smithsonian's Air and Space Museum, Russo spent the last decade training her lens on 100 towers in 23 countries.
"Airport towers are symbolic," she says. "They are cultural greeters... they are choreographers."
She tells the BBC about her new exhibition in Washington, DC
Filmed by Allen McGreevy, edited by Bill McKenna