Line yourself up above it then do a controlled fall. thats how I did it at least. The corners are tricky though.
If hidden is what I think it is, then its very easy.
It's not what you think, then. :P
He is talking about the unlockable secret minigame.
It's still hard. This place to be exact:
(http://img338.imageshack.us/img338/5856/hiddennowall.png)
The star is larger than it looks.