The meeting point
Where the two teams met under the mountain — with tiny error.
GrigorisKoulouriotis — CC BY-SA 4.0 · GrigorisKoulouriotis — CC BY-SA 4.0 · GrigorisKoulouriotis — CC BY-SA 4.0 · GrigorisKoulouriotis — CC BY-SA 4.0
**A kilometre-long tunnel, dug from both ends at once so the two teams met in the middle — in the 6th century BC** — one of the great engineering achievements of the ancient world, and still walked today. The tyrant **Polycrates** commissioned it around **550 BC** to bring water to his city from a spring behind the mountain. The engineer **Eupalinos of Megara** designed it, and decided — rather than going round the mountain — to **go through it**. ⚠ What astonishes is not the tunnel but the method: **digging began from both sides simultaneously**, with the line calculated so the two teams would meet beneath the mountain. **And they did meet**, with negligible error — without compass, maps or modern mathematics. ✅ **Herodotus** himself described it as a wonder in the 5th century BC. ✅ A substantial stretch is **open to walk today** after a long restoration. ⚠ But it is **narrow, low and enclosed** — and does not suit anyone who fears confined spaces.
Where the two teams met under the mountain — with tiny error.
The side trench the water ran in, below the workers' passage.
Letters and numbers cut into the wall and used for measurement.
Pythagoreio, 83103 Samos, Greece
**By precise survey geometry based on triangles and sight lines — not luck.** ✅ **The problem**: to dig from two ends and meet, **you must know direction and gradient to high precision** over a kilometre during which you cannot see the other end at all. ✅ **The likely method**: **surveying around the mountain with a chain of right-angled lines** — the surveyors walk round it step by step recording every turn, building a **notional right triangle** whose ends are the two mouths; **the ratio of its sides gives the angle** each team must dig at. ✅ **Their tools**: sight lines, stakes, cords and a simple water level — **enough**, if executed with patience and care. ⚠ **The clever precaution**: Eupalinos appears to have **deliberately altered both teams' courses near the middle** — each swinging aside, **to guarantee that if they were off, the two tunnels would cross rather than run parallel and never meet at all**. ✅ **That is the most intelligent thing about the project**: a design that tolerates error.
**You experience it as a real tunnel you walked through, not as a picture — and that is the difference.** ✅ **What you walk**: a passage cut into living rock, **high enough to stand in for most of its length** and dropping low in stretches, **with a trench below or beside it** that carried the terracotta water pipes. ✅ **What you notice**: **pick marks on the walls** — individual blows struck by people working here 2,500 years ago; **the cut survey marks** (letters and numbers); **and the deviation near the middle**, where the walls suddenly swing aside — **the point where they met**. ⚠ **What you do not see**: the whole tunnel — **the open route is a portion of it** (extending further or less according to restoration work at the time of your visit). ✅ **Is it worth it**: **emphatically yes** for anyone interested in how the ancients worked — it is one of the few ancient sites you **enter rather than look at**, and standing at the meeting point does not photograph. ⚠ **Not worth it** for anyone troubled by tight, dark spaces — do not force it.
