As military campaigns gradually increased in size and scope, and sieges dragged on into years, the Greeks had to call on all their powers of ingenuity to keep their armies supplied and populations alive. Men such as Eupalinos, from the Corinthian dependency Megara, did much to advance the science of civil engineering. His tunnel, on the island of Samos, was designed to bring water to the people of the city even when under siege. Covering a distance of almost 3,500 feet, the tunnel had to pass through the limestone base of Mount Kastro. It was a mammoth task, but Eupalinos succeeded, where many others had failed, by using geometry to solve the engineering problems he faced. Two teams of diggers, one outside at the foot of the mountain, the other inside the city, followed his careful calculations – all fundamental geometric tenets – to burrow into the rock and meet in the middle. Eupalinos ensured the result by using a technique whereby the direction of each tunnel was changed slightly at a crucial point. This guaranteed that, even with an error of up to two metres, one tunnel would break into the path of the other. Used as an aqueduct for a thousand years, the Tunnel of Eupalinos eventually fell into disuse, but was rediscovered in the 19th century. It has remained a tourist attraction since that time.
