Each week The Gateway goes behind the scenes of the world's major transport hubs, revealing the logistics that keep goods and people moving. This month, the show is in Frankfurt, Germany.
(CNN) -- With 56.4 million passengers, Frankfurt was the world's ninth busiest airport in 2011, according to airport trade organization, Airport Council International.
But when it comes to animal arrivals and departures, the German gateway takes top billing.
Run by German carrier Lufthansa, animals range from domestic pets to more exotic specimens destined for zoos and animal reserves, explains Axel Heitman, director of the Animal Lounge.
"A polar bear was on his way home from the Alps after doing some shooting for some advertising and was really gentle actually," Heitman said.
"He had his owner next to him and he took the entire trailer ... and then we had him transported back to Canada."
The 3,750-square meter facility opened its doors in 2008 and is equipped with non-slip floors and climate-controlled chambers to help make an animal's stay as comfortable as possible.
A team of 60 trained vets and qualified animal handlers are also on hand round the clock to monitor them when they arrive.
"When they are in transit, for example, [the staff] would take them out of the kennels and feed them and if they are here overnight, they will walk them around the facility," Heitman says.
Most animals can travel in the belly of passenger planes, but Lufthansa also has a fleet of 18 freight aircraft which can accommodate all shapes and size of animal -- be it hippopotamuses en route to the Philippines from Israel or rhinos and even crocodiles.
There is no such thing as an average day, Heitman says.
"Every day we learn new things because, as you can imagine, there is a huge variety of animals," he said.