Long before the grid, Karystos was famous for its stone. On the southern flanks of Mount Ochi, between the modern villages and the sea, lie the abandoned quarries that once supplied the Roman Empire with cipollino - a pale marble shot through with wavy green bands, as if someone had sliced an onion and turned it to rock. The Romans called it marmor carystium, marble from Karystos, and prized it. Under Caesar and Augustus, gangs of workers cut enormous monolithic columns straight from the mountainside and floated them out to ships. Those green columns travelled to Rome, North Africa, Egypt, and the Levant. Some still stand in Hadrian's Library in Athens. Walk the quarry slopes today and you find half-finished columns abandoned mid-cut, lying exactly where a crack or an imperial whim left them two thousand years ago.

Four kilometers inland, on a conical hill called Montofoli, the ruins of Castello Rosso brood over the plain. The name means Red Castle, earned by the reddish local slate that glows under the Aegean sun. The Byzantines raised the first fort here around 1030; the Frankish baron Ravano dalle Carceri rebuilt it in stone after the Fourth Crusade. The Venetians coveted it for a century before they finally bought it, then the Ottomans strengthened it further. During the 1821 revolution, fighters including Nikolaos Kriezotis - remembered as the lion of Evia - besieged it again and again without success. The gates did not open to free Greeks until 1833. Below the castle, on the eastern beach, the squat Venetian sea-tower of Bourtzi still stands guard over the harbor.

Up on the bare summit ridges of Mount Ochi sits something no one can fully explain. The drakospita - dragon houses - are megalithic structures built from massive slabs of stone stacked without mortar, held together by sheer weight. Around twenty-three of them survive across southern Euboea, near Styra and Karystos. The largest and best preserved crowns Mount Ochi itself, near the summit at around 1,386 meters. Their roofs are corbelled from converging stone, leaving a narrow slot for light. No one agrees who built them, or exactly when, or why. Temples to the gods? Watch-posts? Their alignment hints at an astronomical purpose, possibly reaching back to around 1100 BC. Locals, unable to imagine human hands moving such stones, decided dragons must have done it.

Modern Karystos is a working town of roughly five thousand people, the kind of place Athenians escape to when the capital grows unbearable. The ferry from Rafina docks at Marmari, and from there the road curls around to the grid by the bay. Its small museum in the Yokaleion Cultural Centre holds Hellenistic and Roman sculpture pulled from the surrounding earth, a reminder that the ancient town of Carystus stood near here too - birthplace of the physician Diocles and the Olympic boxer Glaucus. The whole place is stitched from layers: Neolithic caves at the foot of Ochi, imperial quarries, a crusader castle, a Bavarian street plan. They sit together comfortably, none erasing the others.