I'm open to alternative ideas for that structure, but bear in mind that it should roughly fall between the pyramids and the colosseum. Potala Palace dates to the 17th century and doesn't fit there.
If the timeline around the edge is a timeline, then it would fit more like the Apadana than Potala. Most of the pictures of the Apadana in Susa at least look sort of square-ish buildings. While I can't find any pictures or recreations that really scream AHA that's it, it would at least fit closer on the timeline.