I wouldn't recommend trying that if you're a new runner but what you can do is clip into the observatory by crouching on the top of it (on the slope part) and you should notice Beebo sliding down, then go to the ESC menu and click 'give feedback' and then cancel and you'll clip through, here's a video on it:
Thx but I already know that and I just want to learn a new glitch so do you know how to do that?
There's a second way to do this. When you're on top of one of the trees, spin and immediately pause. Now, look for the door that takes you to New Neocity. The important part is to make sure you have the token menu out and press cancel before you get off of snapshot mode. (~1s to be precise) However, I don't recommend even trying this until you are very close to sub 17. The trick I explained was Neodoor. Watch the top runs and see how they do it.
I do neodoor. Honestly you don't need to be close to sub 17 I would honestly start doing those at sub 19. My pb is an 18:39 and I save time just fine by doing them.