A drop tower or big drop is a type of amusement ride incorporating a central structure or tower. Drop towers vary in height, passenger capacity, lift type, and brake type. Many are custom-made, although there are some mass-produced designs. The most widely sold drop towers have been manufactured by Intamin and S&S Sansei, however Larson International and Funtime have their own drop tower models available as well. Riders initially experience free fall, followed by rapid heavy deceleration.
Read article on Wikipedia