If you jump underneath the basketball hoop with a precise angle, it'll launch you at an extremely high speed and put you out of bounds. You will usually death warp when you do this, but there's a sweet spot where you will be put out of bounds, but not so far as to void. You are then free to explore the buildings and scenery around the level.
99th Opposite OOBDiscovered by OlO_ili, ???
With a precise wallride, you can jump high enough to where the wall doesn't have collision.
Wallride Right-Side PickleDiscovered by OlO_ili, January 2017
By jumping into the wall at a certain angle, the collision of the rail can push you out of bounds. (Not really a pickle, more like an Onion?)
Wallride Left-Side PickleDiscovered by OlO_ili, prior to October 2018
It seems there is an extremely precise area where you can pickle in between the collision for the billboard and the wall.