Instructions
Move left, past the first gear that you find, and jump down to the lower platform.
Continue moving left -- you may descend a large ramp and thin a boulder at the bottom to collect some E-tickets if you wish -- until you encounter a group of green guardians. Destroy the guardians and continue on.
Thin the floor that is beneath the rock pile when you come to it. Then paint the floor back in and cross over it.
Spin-attack the gear on the other side. This will cause the gate to open.