Oooh. Interesting. IMHO, it can’t be the Hellenistic or Mongol empire because while they were big, neither lasted long enough to matter.
I have a soft spot for the Abassid Caliphate centered in Baghdad as they’re the ones that translated and preserved most of the ancient greek and roman knowledge that survived into the modern day as well as persian. So much of what fueled the renaissance and enlightenment was only possible because of the Abassids. Unfortunately, the rise of Islamic mysticism, the Ottoman Turks, and the onslaught of the Mongols ended them.
I actually think the Roman empire is overrated in terms of scientific advances. Yes, they had a huge influence, but they built alot on the ideas of the Greeks. They were great in some ways, I just think there’s a romanticism that people have about them that doesn’t really line up with the reality.
The British Empire deserves some praise. Contrary to what DigDug said, they did not treat their colonies well at all. But many of the innovations of the enlightenment did come out of it. The Scots deserve alot of the credit, but the modern iteration of democracy was kind of birthed out of this Empire.
But I have to pick one right? I guess I’ll go with the Abassids just to be contrarian.