When we were near the airport, our driver told us about an air show here in 1999, and that airplanes fly-through the hole here. Below is a description of the area from the air show organizer's web site.
"Eight kilometres south of Zhang Jia Jie City proper stands a solitary mountain 1'518 meters above the sea level. It looks like a huge platform, with precipitous sides. On the Eastern side there is a huge cavern that runs south and north like a gate, hence its name Tianmen (the Gate to Heaven). The gate is 132 meters high, 37 meters wide and 70 meters deep. At the foot of the Mountain lies the Zhang Jia Jie airport."