OK I don't think anyone will get this.. without cheating anyway..
It is the Deer Cave in Borneo
From a website about BorneoDeer Cave is the world’s largest natural rock chamber that can contain London’s St. Paul Cathedral five times over and accommodate 40 Boeing 747s side by side. It is accessible by plank walks through the jungle and by lighted paths throughout. At 5pm each day, over 1 million bats blacken the sky as they depart Deer Cave in search of food.
I seen this on a TV show called planet Earth the other day 😛