Eupaline tunnel - the legacy of an ancient architect (7 photos + 1 video)
Underground construction work is much more difficult to carry out compared to above-ground construction. But ancient architectural monuments that have survived to this day prove that if you have the desire and the skills, you can create something masterpiece and functional. 
Some researchers call the Eupaline or Samos Tunnel, located on the Greek island of Samos, a kind of wonder of the world. The local engineer Eupalinus from Megara built it by order of the Samian despot Polycrates, who seized power on the island. 
An underground water supply was installed to ensure water supply in the event of a siege of the main city (Pythagorea). The uniqueness of the structure lies in the fact that it was dug from different sides - using the counter-laying method. And it turned out great: the diggers met with minimal divergence. It was 10 meters horizontally and 3 vertically. Even in the last century, when using preliminary calculations and the availability of equipment and technology, the indicators were often worse. 
Eupalin used only the basic principles of geometry during his calculations. And since this was in the 6th century BC, even before Euclidean geometry there were still several hundred years left.
Such accuracy was achieved due to the fact that at the approximate meeting point the direction of both tunnels was changed by a slight angle. It turns out that they would intersect even at a considerable distance. 
As for the vertical deviation, the problem of error was solved in a similar way: in one tunnel the floor remained at the same level, but the ceiling rose, and in the second the ceiling remained at the same level, and the floor lowered.
Researchers believe that the Samos Aqueduct was used for a whole millennium, and then was abandoned. Interest in the engineering object intensified only at the end of the century before last. 
Now this amazing masterpiece of ancient architecture is open for tourist excursions and allows people to feel the spirit of an ancient solution that, if necessary, can function in our time. 
