My vote goes to an empire not on the list: the Ancient Egyptian Dynasties, in particular, the Old Kingdom or Kingdom of the Pyramids.

From them we get some of the world's earliest literature, advanced mathematics (which the Greeks borrowed heavily from), early forms of practical medicine, technology such as the ramp, the lever, rope trusses, paper, and of course.......the Pyramids and all they entail (mathematics, astronomy, and engineering).