This episode suggests that various sites around the world; such as Göbekli Tepe in Turkey; the Incan ruins of Sacsayhuamán in Peru; the Carnac stones of France; and Zorats Karer in Armenia, show construction techniques and mathematical concepts that were not believed to have been known at the time, and that this knowledge was gained from alien visitors.
More on unexplained-mysteries.com and a Index of Prehistoric and Sacred Monuments on Ancient Wisdom