People of the past were quite smart, despite not having access to the Internet or modern technology. Case in point: the Antikythera Mechanism.... proof that gadgets have existed for thousands of years. In fact, you could even call it a "computer" because it operated as a complex mechanical computer system that tracked the cycles of the solar system.
Here's a fun infographic detailing five of the more impressive feats of ancient engineering:
Here are the top 5 amazing feats of ancient engineering:
Great Pyramid of Giza
Great Wall of China
Statue of Zeus at Olympia
Banaue Rice Terraces