Supraland

Whilst on your way to the blue crystal, after the area where you hand off the red barrels, you go up wooden stairs. there is a cave to the left that you open with a purple box button. In there you find a prison, go in and open both doors, the doors have a little ledge on top so now you can jump across them and around the corner. With some jumping and climbing on this building you can get to the upgrade chest