When building an airport, it is always a good idea to place it in a wide, flat area that is free of obstructions and easy to access.
Or in between two 18,000 foot mountains in the Himalayas. Whichever.
Pilots need to maneuver between mountains, fly within feet of houses, and land on a narrow, 6,500 foot runway. Planes are only allowed to take off and land during the day, since any flying at night has been deemed far too dangerous.
Strong winds can whip down from the mountains and easily send a plane off course. Because of the danger, only eight pilots in the world are qualified to fly in and out. And they transport a lot of people.
As there is only one other airstrip in Bhutan, about 30,000 people come through Paro Airport each year.
But seeing is believing. Check out this video of a landing below to see just how difficult it can be (YouTube via Newser):