There have been many ancient civilizations which have lived, which we know about and which we do not.
Some would argue that Atlantis (9600 BC) or Lemuria(24000 BC) where the smartest as well as the oldest, but that would be another topic for discussion.
According to "documented" History I would have to say the Egyptians (7000 BC) where the smartest compared to Mayan (2000 BC) and Aztecs (1200 AD). And some say a lot of Egyptian knowledge and mythology came from Atlantis or Lemuria? Then again, a lot of todays beliefs, knowledge and relgion is just old beliefs modified and re-branded.
Yes they were able to do amazing things, as they were "in-tune" with the Universe. The Shamans/priests could connect to the Origin/Source for the answers they seeked. We are able to do the same through practice of meditation.