The drowned quarry
Terraces and half-cut marble blocks above and below the water.
Ronald Saunders from Warrington, UK — CC BY-SA 2.0 · Jean Housen — CC BY-SA 4.0 · Jean Housen — CC BY-SA 4.0 · Jean Housen — CC BY-SA 4.0
**A small peninsula with two beaches back to back, and an ancient marble quarry running into the sea** — in southeastern Thassos, and the finest thing on the island. ✅ **The formation is unusual**: a small peninsula joined to the coast by a narrow neck, **with a sandy bay on either side of it** — **so if the wind gets up on one, you walk two minutes to the other**. **A genuinely practical advantage.** ⚠ **What makes it exceptional is the quarry**: marble was cut from this headland from the **7th century BC**, **and the quarry is still there** — **terraces, steps, half-cut blocks and column sockets, some of them directly underwater** after the sea level rose. ✅ **So you swim above the workings of an ancient quarry** — and see the blocks on the bottom. ✅ There are also **two early Christian basilicas** with columns on the headland.
Terraces and half-cut marble blocks above and below the water.
Sandy bays back to back either side of a narrow neck.
Early Christian churches with columns on the headland.
Alyki, 64002 Thassos, Greece
**Because sea level relative to the land changed — a combination of the ground sinking and the sea rising.** ✅ **The first fact**: **the marble was cut above water** — nobody quarries stone while submerged; **so the terraces, steps and column sockets you now see underwater were dry** when they were worked. ✅ **The first cause — subsidence**: this region is **tectonically active**, **and the coast is slowly sinking** over the centuries through earth movement and earthquakes — **usually the larger factor** at drowned sites in the Aegean. ✅ **The second cause — global sea-level rise** since antiquity, **smaller here** but additive. ✅ **The result**: **the ancient shoreline lies deeper than today's** — so what was a loading quay for ships is now seabed. ⚠ **This is common in Greece**: many sunken towns and harbours (Pavlopetri, ancient Epidaurus). ✅ **What it means for you**: **you swim over a real worksite** — seeing **chisel marks** and the wedge slots the blocks were split along, **perfectly clear in clear water**.