What triggers the opening of the path to World 4?

[CheatoRomani]

Hi there,

I just realized that above the book to World 3 (going up using the Lizard Lash) there is a room with a huge entrance leading to World 4.
Has this entryway been there before? I could swear I have been there searching for an entryway before.

Any clarification deeply appreciated

[Hopix]

Is that the entrance made out of red piping? If so, yeah, it's always been there.