A nice, expensive megastructure for the late-game Seleucids, Baktrians or Parthians to build (whoever ends up in control of the area). I'm not exactly sure what it would do though (rebel reduction through loyalty/law bonus?). Probably it would be best if built in steps.
It's interesting that people there think this had something to do with Alexander, even thoughhe was dead after it was built. Just shows how important a figure he still is in popular culture in that part of the world.