Eupalinos

Eupalinos or Eupalinus of Megara was an ancient Greek engineer who built the Tunnel of Eupalinos on Samos Island in the late 6th century BCE. Though the construction of the tunnel has been attributed to the tyrant Polycrates of Samos, it is now considered to be a later construction and having been built between 550 and 530 BCE. In any case, the tunnel was, and is, regarded as a major feat of engineering.