I went through several ideas. Originally I was going to have a pendulim from the center the player would have to reach and slide down. I thought of a world of abandoned time pieces. This is my latest idea.
Tempis will have four different clock faces representing four different planets in the local system. Scattered around on the surface will be telescopes, three for each of the four planets. The player will record the numbers then enter the clock. A giant planetarium will be in the center. Entering the numbers will unlock a book to each of the other planets and correct the position of the planetarium and the time on one of the clock faces.
Here is another image of the inside to give an idea of the scale.