At least I think it's the mechanical age. I got there from the sunken gear. When I cross the bridge and go in the round building, I find very little that does anything of note. A bird that flaps its wings, a cobra-in-the-box, jewels that light up when I touch them. Some sort of model of this round building, that makes noises that are supposed to be some kind of code, but I can't figure out what they correspond to. An underground room with controls for a rotating elevator, but it only seems to have one useful position, and when I go up in it I find nothing. At the middle setting, I can't even exit the elevator. It seems this building oughta rotate, so I can go somewhere else, but I can't figure out how. Also there's some sort of control right next to where I enter the age, but I can't find any clues for this either. And I have no idea how to go back to Myst Island.

The in-game hints aren't working for me. Maybe if I had a transcription of them, I could figure this out?

1) Look very carefully around the big seats ("thrones") in both of the chambers. There's something that easily escapes the eye.

2)After going up in the elevator, and pressing the middle button, have you noticed that it takes quite a while before the elevator goes down again?

Thanks for the hints, they weren't too much. Got four pages now!