The Tunnel of Eupalinus (or the Eupalinian Aqueduct) is a monument dedicated to the science of geometry. The tunnel “manages” to glorify geometry, as did the Temple of Artemis, one of the Seven Wonders of the ancient world. The Tunnel of Eupalinus is the work of a genius in geometry, at a time when geometry had just made its first “celestial” leap.

From a theoretical point of view the Tunnel of Eupalinus is a huge project, because the geometric knowledge and instruments were still elementary at the time it was build. The whole project was dazzled by a charismatic creator named Eupalinus and will be mentioned in the centuries to come as one of the greatest achievements of Ancient Hellenism.

On the occasion of its first opening for the public and our recent visit (we actually walked the tunnel all the way), we would like to make known some facts, most of which are quite impressive yet unknown to the many!

The Tunnel of Eupalinus: A Wonder of AntiquityBeyond its length, its purpose and the name of its creator, WHO knows, for example, how much money it cost? How many years took to complete? Who knows it’s two-edged and especially its rectilinear form and shape?

The evidence and the facts cited below are based on an excellent book published by the mathematician and architect Dimitris Tsimpourakis, titled “530 BC: The Tunnel of Eupalinus in Ancient Samos”.

Our aim is to make known these facts to as many people as possible in order to stimulate interest and to attract more visitors.

Samos has been inhabited since the ancient times and its contacts with the cultural centers of Ephesus and Miletus, in the opposite Asia Minor cost, have been constant and intense. Samos’s contribution to geometry was through Pythagoras (580-500 BC) and Aristarchus (320-250 BC). At the end of the 6th century BC, political authority passed to a nobleman called Polycrates, who ruled the island as a tyrant from 537 until 522 BC, which turned to be an era of great prosperity for the whole island. According to Herodotus Samos under Polycrates became “the first of the first among the Greeks and barbarians”.

The Tunnel of Eupalinus: A Wonder of AntiquityHerodotus in his “Histories” (3rd Book) quotes:

“I have written at such length of the Samians, because the three greatest works of all the Greeks were engineered by them.

The first of these is the tunnel with a mouth at either end driven through the base of a hill nine hundred feet high; the whole tunnel is forty-two hundred feet long, eight feet high and eight feet wide; and throughout the whole of its length there runs a channel thirty feet deep and three feet wide, through which the water coming from an abundant spring is carried by pipes to the city of Samos. The designer of this work was Eupalinus son of Naustrophus, a Megarian.

This is one of the three works; the second is a breakwater in the sea enclosing the harbor, sunk one hundred and twenty feet, and more than twelve hundred feet in length.

The third Samian work is the temple, which is the greatest of all the temples of which we know; its first builder was Rhoecus son of Philes, a Samian. It is for this cause that I have expounded at more than ordinary length of Samos”.

Herodotus, who wrote his “Histories” some 80 years after Polycrates’ death, dedicates many pages to Samos, especially during the period when the island was ruled by Polycrates, and at the end of his work is clearly admirably, but dense, when he comments on the three abovementioned projects. This confirms, indirectly but clearly, that these three explicit projects were completed when Samos was indeed “the first of the first among the Greeks and barbarians”, i.e. during the years of Polycrates.

The Tunnel of Eupalinus: The First Acquaintance

The Tunnel of Eupalinus is a 1.036 meters long tunnel (in straight line) built around 530 BC by the architect Eupalinus from Megara. The extraordinary thing is that the excavations of the tunnel began (according to one account) at the same time from two opposite sides, which met with minimal divergence. The construction lasted about 11 years. The tunnel follows a horizontal direction. A sloping groove was opened in the floor, in which clay pipes were placed and used to carry the fresh water to the city. From the source (spring) the water was carried by an underground, 853 meters long, pipeline to the northern entrance of the tunnel and, by clay pipes, through the tunnel, to the city.

The Tunnel of Eupalinus functioned as an integrated aqueduct system until the fifth century AD. Since then its maintenance was neglected and eventually abandoned, due to the operation and use of another aqueduct, built by the Romans, which covered the needs of the city for fresh water. The abandoned tunnel was blocked by dirt and stalactites, and eventually collapsed after serving Samos for more than 1.000 years. In the seventh century AD it was re-used as a cemetery this time. But again, after several centuries, it was abandoned and completely forgotten. It was re-discovered in the mid-19th century. The discovery was made possible thanks to Herodotus since no one else ever wrote anything about the Tunnel of Eupalinus. Indeed, in 1856 the French archaeologist Guerin discovered, with the assistance of a local Chieftain named Alexis, the spring and the beginning of the tunnel.

Are you aware of the following stunning details?

Note: In order to understand some of the information listed below is necessary to use the drawings posted as figures. Our references in the text are based on their numbering (Figure 1 or Figure 2 etc.).

  1. The southern part (400 meter long) and the northern part (265 meters long) of the tunnel are rectilinear.The Tunnel of Eupalinus: A Wonder of Antiquity
  2. At the meeting point of the two opposite tunnels appears a notable difference in direction as well as in the level of the floors and ceilings. This differentiation shows the two-edged form of the structure.
  3. The altitudes of the two entrances (at 55,83 meters in the northern slope and at 55,26 meters in the southern slope) clearly indicate the choice of Eupalinus to construct the two tunnels on the same horizontal plane.
  4. After the construction of the first 400 meters the southern tunnel turns abruptly 34 degrees to the right and continues for 30 meters more. The turn was not made at the middle of the distance but 135 meters before.
  5. If the opening of the two opposite tunnels had been started at the same time, given the fact that the meeting point is located before the middle point, the construction of the southern tunnel would have been stopped two years earlier, something which didn’t happen.
  6. Thus, is highly speculated that the construction of the southern tunnel began later than the northern one (one and a half years ago).The Tunnel of Eupalinus: A Wonder of Antiquity
  7. The awkward and inexplicable maneuver (Distance KA, Figure 38), the right turn towards point A and the crooked movement from Point A to Point B can be interpreted by a bold assumption: At some point the northern tunnel met a narrow, natural, horizontal, 150 meters long cave. In order to overcome this unexpected encounter, Eupalinus decided to abandon the artificial rectilinear course and “follow” the natural course of the cave by widening and shaping it appropriately. By doing so he gained 136 meters or more than two years of work (the widening and shaping of the cave took 5-6 months to complete).
  8. Points A, Θ, and Β are synergistically (Figure 38).The Tunnel of Eupalinus: A Wonder of Antiquity
  9. ABΔ triangle is isosceles (Distance AB is 137 meters long in straight line or 139 meters in crooked line, Distance ΒΔ is approximately 139 meters long). This fact confirms that in 530 BC the three angles of a triangle theorem was already known.The Tunnel of Eupalinus: A Wonder of Antiquity
  10. Eupalinus reached Point B during the seventh year of construction (Figure 38).
  11. The ΛΕ section (Figure 44) isn’t the product of a geometrical study but the result of the natural joy and comfort of Eupalinus and his crew upon the completion of a ten-year long effort. This is because at Point Λ the northern crew heard the hammer knockings of the southern crew for the very first time. The knockings led them to turn rightwards. The Tunnel of Eupalinus: A Wonder of Antiquity
  12. All the attempts for the meeting of the two tunnels were made by the northern crew. The southern crew either waited or proceeded slowly, always producing sounds signals (hammer knockings) to alert the northern crew.
  13. A careful observation of the topography from Point Λ to Point Z (Figure 44) gives the impression that the two tunnels were “searching each other”. The Tunnel of Eupalinus: A Wonder of Antiquity
  14. The elevation study shows that the floor of the southern tunnel at Point E is located at an altitude of 55,17 meters, while the northern tunnel, just before Point Π, is located at an altitude of 55,48 meters. Thus, for more than 1.000 meters, the level of the two floors remains almost completely horizontal.
  15. Shortly before Point Π (Figure 44), 27 meters before the meeting point of the two tunnels, a vertical maneuver begins at the same time with the horizontal one (guided by the hammer knockings, as mentioned before). It seems that Eupalinus, while certain for the correct direction of the two tunnels, began to fear that one tunnel might pass over the other. So he decided to increase the height of the northern tunnel, in order to increase the chances of meeting in case the two tunnels were not coplanar after all.
  16. Following the completion of the tunnel, Eupalinus began the construction of the sloping groove on the floor, which would transport the water to the city. This is what Herodotus called the “twenty-cubit”.
  17. In the northern tunnel the groove was located 3,5 meters below ground, while in the southern tunnel its depth reached 8,5 meters below ground. This sloping groove was built by workers who worked kneeling, under icy conditions, in darkness, and in abundant underground waters. Today, the view of the groove looks awesome and inspiring due to its depth and tightness.
  18. The outer southern part of the aqueduct is located 5 meters below ground and has a 0,55% gradient. Today only few remnants are preserved. The Tunnel of Eupalinus: A Wonder of Antiquity
  19. The volume of the excavated soil was enormous. Today is estimated at about 16.000 m³.
  20. In the spring area (Agiades) a rectangular triangle-shaped basin was created with the construction of the two vertical sides and the sculpturing of the hypotenuse on the rock. Its dimensions are 7 by 5,5 meters. Inside the basin, 15 square stone columns were built on top of which were laid stone beams and on top of the beams were placed thick stone plates. So the water tank was housed and clean water was ensured. Today the basin is preserved exactly as it was built and its roof now serves as floor to the small church of St. John. The spring still supplies fresh water carried to the city by modern metallic tube (400 m³ of fresh water per day).
  21. The water was channeled to the city by high quality clay pipes. The pipes were cylindrical with 20 cm internal diameter and 3 cm thickness. The length of a single pipe was approximately 67 cm and every second pipe had a top hole, 15 cm in diameter, for ventilation, easy maintenance and cleaning.
  22. The small gradients of 0.5% (theoretically carry less water) show that the underground pipeline (from the spring to northern entrance) began construction long before the completion of the northern part of the tunnel. That is why the underground pipeline was 3,5 meters below the floor when it reached the northern entrance.
  23. The construction speed of the tunnel was 4 meters per month on both tunnels.
  24. The Tunnel of Eupalinus: A Wonder of AntiquityOverall the tunnel took 11 years to complete.
  25. While we are grateful to Herodotus for his reference to the Tunnel of Eupalinus, we must “reproach” him because he didn’t record more details about the project, especially for the period it was constructed. So we have to accept that it was constructed when Samos accumulated wealth and enemies, when the City constructed the two-stadion breakwater for its triremes, and when the City was surrounded by a 6 km long wall, i.e. during Polycrates’s rule. It is speculated that the Tunnel of Eupalinus began construction around 534 BC and was completed around 523 BC. Polycrates was murdered in Sardis in 522 BC. So he might not have the chance to see his famous aqueduct completed.
  26. Accounting for its total cost, we have to make some risky assumptions. We accept the assumption that professional craftsmen were employed due to the precision requirements of the whole project. We also accept the assumption that the project was done in three shifts per day (for digging) and two shifts per day for the construction of the outer parts. The productivity of the so-called “continuous worker” (i.e. the total work produced by the three shifts inside the tunnel) is 2 meters per tunnel per month (4 meters in total). The wage of a worker was 1 drachma per day (in Classical Athens the wage of an average craftsman was 1 drachma or 6 obols per day, a theater ticket cost 2 obols, a pair of sandals 2 drachmas and a small house 700 drachmas approximately). In total, the amount of drachmas needed corresponds to 222.000 wages. Given that an Athenian talent of gold (or Athenian standard) weight 22,6 kg and is the equivalent of 6.000 drachmas, we conclude that total labor cost was 52 talents of gold (52 x 26,2 = 1.363 kg of gold). It should be noted that a well-known Athenian doctor was paid for his service, by the City-State of Athens, 20-30 drachmas a day or about 1-2 talents of gold per year. The same amount was paid for a young, beautiful and educated prostitute.
  27. We should not forget Aristotle’s view that the great public works made by tyrants aimed at taxation and employment in order to secure and maintain public order and avoid possible conspiracies. In other words, Aristotle was convinced that the predominant concern of all tyrants was employment or low unemployment in order to maintain their tyranny (authority).
The Tunnel of Eupalinus: A Wonder of Antiquity
Coinage under Polycrates
  1. The question is why Polycrates and Eupalinus choose the underground route? A circumferential route from the spring to the city’s reservoir would have a total length of 3.370 meters and would be constructed within a year, while the underground route took 11 years to complete. So the circumferential route would be quicker, cheaper, safer and more practical in slope arrangement. However, for some reasons, that we’ll never know, Eupalinus chose the underground route.
  2. Polycrates accumulated wealth and, following the common practice of most tyrants, turned his attention to great public works, for glory and employment. Polycrates’ public works were large in size and aspired to be the largest in all Greece. For example, the Temple of Hera with its 155 columns and the 450 meter long jetty was actually the largest temple in Greece. The Temple of Hera, which was never completed, was enormous in size for the ancient Greek standards. In comparison, Parthenon, of the powerful and wealthy Athens, was built 130 years later and had only 46 columns.
  3. Assumption No.1: Until then the most famous fountains and aqueducts in Greece were: (a) The Fountain of Theagenes, Tyrant of Megara (b) The Peirinis Fountain of Periandros, Tyrant of Corinth and (c) The famous Nine-Spout Fountain of Athens. Polycrates wanted to surpass these fountains in order to glorify himself and Samos, “the first of the first among the Greeks and barbarians”, according to Herodotus. The 3.400 meter long pipeline of the circumferential route wouldn’t cause Pan-Hellenic admiration. Thus, the underground route was both an exciting and tempting idea. Expensive, time consuming, but amazing! Polycrates was charmed, despite all the troublesome issues, and finally ordered its construction. And if we judge by the words of Herodotus, he did cause admiration.
  4. Ironically, Herodotus, as a non-expert, was impressed by the two-edged form of the tunnel, not by its rectilinear shape which probably ignored or he was never informed about it, despite the fact that the rectilinear shape was the most amazing think of the whole construction and for this Eupalinus decided the most complex of all the available solutions, i.e. the underground route.
  5. Assumption No.2: Eupalinus chose the most difficult solution, in geometric and technical terms, not out of superficiality or ignorance but out of ambition to establish himself as the greatest engineer of his time.
  6. The Tunnel of Eupalinus: A Wonder of AntiquityThe Tunnel of Eupalinus was discovered in 1882 while its rectilinear shape was acknowledged in 1884 by Fabricius. Herodotus, in his short description, does not refer to the straight line of the tunnel, although this was the most amazing of its features. Herodotus lived for a long time in Samos (as an exile), when in his hometown (Halicarnassus) ruled a close friend to the Persians, the tyrant Lygdamis. During his stay in Samos he surely visited and explored the tunnel which already operated as an aqueduct for at least 60 years. With his own eyes he must have seen the rectilinear shape and the two-edged form of the tunnel. It seems, however, that no one spoke to him about the rectilinear shape of the tunnel or someone did it but he questioned the information because he couldn’t verify it with his own eyes. Even today, due to the complex central maneuver, the visitor is unable to acknowledge the rectilinear shape of the route. So Herodotus didn’t see or didn’t find the rectilinear shape of the construction. After 2-3 generations, this characteristic feature was forgotten. It was made known again 24 centuries later, in 1884.