Special devices, which simulate the experience of freefall, are a perfect tool to find out what skydiving feels like without jumping from an airplane. They are capable of generating sufficient airflow and certain conditions that keep this flow stable and usable for simulating skydiving.
Airflow is created inside a big vertical cylinder known as a wind tunnel.
“Vertical wind tunnels are used to practice for free fall (indoor skydiving or bodyflight), while virtual reality parachute simulators are used to practice parachute control”.
(Source: Wikipedia)
Skydiving wind tunnels work by either pushing the air up from below or sucking it up from above using huge air fans. The experience is the same in both types – the wind is rushing up at you, holding you as you learn to maneuver your body through the air.