This tunnel is something special for sure! In the 6th century BC, the population of Samos was growing rapidly in the harbor that is in Pythagorian Village. Unfortunately the best source of fresh water was a spring on the other side of the island with a mountain in between. It would have been possible to build a series of connecting channels around the mountain however those would be prone to blockages and would be much longer than if they could go through the mountain. Remember, this was 600 years before Christ! Epalinos devised a plan to dig a tunnel through the mountain. Compasses and topographical maps had yet to even be invented. The final complete system was approximately 4000 feet long. Another thing that makes this tunnel unique compared to other tunnels at the time is that this one was dug from each direction and they met in the middle. No one is certain how exactly they managed the feat of meeting in the same place both vertically and horizontally. It is speculated that they used markers along the top of the mountain to ensure the line horizontally matched up and the horizon was used to ensure the vertical distances matched. To build the tunnel, they used slaves (no surprise there) from Paros. As the story is told, they took 12,000 slaves from Paros and told them if they could live to the end they could go home. After 10 years, 250 people survived and went back home. Archeologists do know that they first dug a tunnel utilizing some of the first known air shafts. Once the tunnel was dug, they were able to go back through and dig the actual water channel down below. Ceramic pipes were used in the water channel. The builders had to make sure that the water didn’t move too fast and cause chalk to accumulate in the lines. The vertical difference between the spring side and the harbor side of the tunnel is 2 feet. They determined that a fall of 0.46% would solve the problem provided a flow that was neither too fast nor too slow. Lastly the tunnel was meant to be a secret so that it could be used for defense of the island. The island Proximity to Turkey (Asia Minor) made it prone to attacks. The tunnel allowed soldiers to enter one side of the mountain and come out the other undetected.