Planet Earth is home to some spectacular relics from bygone eras, constructions that seem to defy the technological capabilities of their time either because they’re too big, too heavy, or too complex. A technologically Advanced Alien Civilization must have lived on one of the Earth before disappearing without a trace. Evidence of Advanced ancient technology and ancient artifacts has been discovered all over the planet, hinting that were left behind by the aliens. But most of the evidence of these civilizations has been hidden from the public.
More traces of these ancient aliens are most likely to lie beneath the ground. Ancient Structures buried beneath surface might survive and be discoverable. Such discoveries might occur using the tools of the burgeoning field of the archaeology. So does this explain how prehistoric civilizations managed to make some of the largest and most enigmatic constructions on Earth?