The Slide technique
Once the player is on top of the Big Pointy Building, they should not grab the parachute. When the player then jumps from the Big Pointy Building, they will move towards the tower, and will eventually slide down on it slowly. This is a glitch and is related to how sloped surfaces work in the game's physics engine.
Ironically, if the player attempts to use the parachute and simply jump off without pulling the chute, the player will die.