The Aqueduct of Efpalinus is one of the largest engineering projects constructed in ancient times. The purpose of its construction was the water supply of the ancient city of Samos (modern Pythagoreion).
This is a 1036 meters long tunnel which was built in the 6th century BC by order of the tyrant Polycrates of Samos. The construction was entrusted to the mechanical Efpalinus from Megara and lasted about 10 years.
The first mention of the tunnel in antiquity was made by Herodotus, who while visiting Samos stood out among the marvels of the Samians like the Heraion, the wharf of the city of Samos, the Polycratean walls and the Aqueduct of Eupalinos. Heron of Alexandria also reports this in his book "Dioptra".
The need to build the project was created when the water supplying the city was not enough, and the water springs (the current location Agiades) that could solve this problem were outside the walls and behind the ridge of the mountain (the current Kastri) that protected the city from the north. Therefore water should come to town or around the mountain, either through it. Polycrates also wanted this pipeline not to be visible, so at long siege of the city, there wouldn't be a problem in water supply for the residents. Eupalinos finally decided to pass the tunell through the mountain.
The intelligence of Efpalinus is seen from the data that he had to set and calculated on the portion of the pipeline that would pass through the mountain. That is:
- The tunnel had to be horizontal (no slope) to avoid any problems finding groundwater
- It had to be straight (no turns), to have the shortest possible length
- Simultaneous drilling from both sides of the mountain, to minimize construction time
- It had to be a certain height, because of the altitude that were the water springs.
The accuracy with which eventually he constructed the aqueduct is amazing even by today's technology. Experienced scientists dealing with construction projects of large tunnels around the world are also surprised in the design of this ancient aqueduct.
Characteristic of the construction is that the tunnel was opened simultaneously from both sides of the mountain. That's the feature, Herodotus called it "amfistomo orygma". The amazing thing is that the workers who undertook the excavation of the tunnel started from both sides of the mountain and met in the middle of the path with great accuracy, which makes this task wondrous feat of engineering and technology.
The tunnel was constructed horizontally and directly under the floor was opened a inclined groove where clay pipes were placed for the flowing water. The opening of the tunnel is approximately 1.80 x 1.80 meters and is 55 meters above sea level and 180 meters below the summit of the mountain. The hydraulic project was constructed in three sections. The first part included the pipeline that started from the springs and ended at the mountain, the second part was the tunnel that was drilled into the mountain and the third section connected the end of the tunnel with the collection tank of water located within the city.
The aqueduct ran for over a thousand years until because of failure maintenance it became obsolete in the 7th century AD.
Currently, a small part of the tunnel can be visited and is located on the side of the mountain that overlooks the Pythagoreio.