The last thing you would expect to find in an ever-expanding city like Beijing is Wildlife. But it's here!
In fact Beijing has a greater variety of bird species than London, New York and Paris.
This eight part series will explore Beijing's wildlife and the people trying to conserve it.
In Part 5 Professor Gao Wu talks about Beijing's historic relationship with the swift. And how this migratory bird has been managed to adapt to Beijing's changing urban environment.