Spoiler : As I didn't have GLH, astro was not only meant for invasion but also for much better trade routes. However I was shocked how many centuries it took to leverage that tech advantage. It's true, the AI techs very slowly on that map. Could still go for Space, it's not lost yet, but I should at least hurt Charlie before because he is at tech parity. How did you realize culture without marble? I find it extremely difficult without having Sistine and/or Parthenon.