I'm stuck on building the mega obelisk -- I've tried looking for upgrades on every type of obelisk/ crystalisk, checking the build menu, even trying to merge obelisks in various configurations. I'm stumped! Any help would be greatly appreciated!

Click on the house you want to move, then click “move” — it’ll show a red circle around the pyramid and you can just move the house outside the circle.

When you click on a house to move it there should be a red circle around the pyramid. You can then just move to a new spot outside that circle.