Several points.
1) There is currently no vacuum, no space that has nothing in it, Alfin Stratos having filled all with Aether, the first song, the melody of creation. Confirming you wish to remove all existing matter from the location of the clock-tower?
2) Do not assume that your laws are inviolate... even under threat of annihilation.
3) Sealing off the clock-tower from outside interference is a no go. Something will at some point make it's way there, depending on my whim or the actions of other gods. You can attempt to make access harder, but take note of this.
4) Similarly, indestructibility is likely a pipe-dream.
4) What is the foundation upon which the tower is built? Nothingness?
5) I'm leery of granting mortals knowledge that easily, but I'll see how I feel about it when I write out the update.