[Bungleau]

That's a piecemeal puzzle... you flip levers in one spot to gain access to another, where you can flip more levers to gain access to a third spot, and so on.

I don't remember the door with the button, but there are a couple of sneaky tricks you can use if you're stuck.

First, you don't have to raise all the floor pieces. Time it right, and you can jump over an open piece of floor, letting you get to where you want to be.

Second, if you line it up right, you can actually climb up the chains. Look up, jump up on them, and keep going up. When you get near the top, jump onto the landing.

If you check the Best Tips thread, I believe that the pattern for flipping the levers to raise all the platforms is listed in there. You might have to search for it, though...