PHILADELPHIA - When a full-grown Amur tiger peers down on people just a few feet below, it's a new experience for cats and humans alike.
The Philadelphia Zoo, America's oldest, is unveiling an exhibit that allows its large cats to walk along enclosed, overhead trails that span the zoo's pathways.
The new walkway officially opens on Saturday, but two tigers Wiz and Dimitri have already tested it a few times.
They had never encountered humans at anything other than eye level before, said Ms Kay Buffamonte, lead keeper of the zoo's Big Cat Falls exhibit. "Being elevated for them is a position of power," she said.
Once inside, the two cats like to run, said Mr Andy Baker, chief operations officer of the zoo. "I've seen them get up to pretty high speeds," he said.
Visitors seem to be enjoying the unusual close encounters.
"At first I was like, 'Whoa,' and then I thought it was cool," said Emerson Singer, 6, of Philadelphia who spent Wednesday at the zoo and got a preview of the new exhibit.
The project, featuring mesh-enclosed walkways just 14 feet above the ground, is part of an initiative to give animals more room to walk, run and explore.
Zoos nationwide have tried various strategies to build habitats that may help animals escape the boredom of a confined space, said Mr Jon Stefansson, a Philadelphia-based architect whose firm CLR Design helps zoos create habitats.
At the Dallas Zoo's Giants of the Savannah exhibit, elephants, giraffes and impalas share a common space, he said.
At the Smithsonian's National Zoo in Washington, orangutans travel between two habitats by swinging on ropes high above the ground.
Other zoos use smaller systems of trails, but the Philadelphia Zoo is aiming eventually to link trails across its entire 42-acre campus.
The cat exhibit is its third trail system. Small primates such as pied tamarinds move along a suspended mesh tube known as the Treetop Trail roughly a third of a mile long, and orangutans have domain over the Great Ape Trail.
So far the Big Cat Crossing is just 330 feet but plans call for it to be extended. Lions and snow leopards will use it as well.