On the slopes of Kallimani stands Kastri, named for the medieval castle whose ruins crown the mountain. It was not alone. From the Kastro you could see the Castle of Dragoneras, the Tower of Kipon, and others scattered across the region, and at night these strongholds talked to one another by torchlight, a chain of signal fires flickering across the dark hills. In the tense years before the 1821 revolution, the villagers of Oktonia fled to these fortresses when the forces of the Pasha of Karystos came. The castle held until betrayal opened it. After a treasonous act, it was besieged and bombarded; the women and children escaped, the old and the weak were killed, and the fighters slipped into the mountains to regroup. In revenge, the attackers burned the monastery and the country around it.

Below the castle stands the church of St. Demetrios of the Waterfall, and its walls hold a quieter testimony than the burned mountain. The monastery that once stood here was a center of the independence movement, a place that inspired fighters and supplied the revolutionary ships anchored in the sea of Markourio. That role cost its abbot, Paisios, his life: he was captured and executed by impalement, a death meant to terrify as much as to punish. Inside, the church is covered floor to ceiling in post-Byzantine paintings from around 1600, dense with religious scenes rendered in vivid, original color. In 1921 the Greek state declared it a Prominent Monument, ranking it among treasures like the monasteries of Daphni and Hosios Loukas.

Oktonia is a place of water and stone. Ornate fountains, some old, some new, are scattered through its four settlements, each with a name and a story: Marinou, Sgourou, Voivonta, Soor. Along ten kilometers of coast lie quiet beaches, and the hills are riddled with caves. Some sheltered villagers fleeing the Turks, who waited along Cape Punta for a passing Greek ship to carry them to safety. Others hold deeper time still: in caves around Kallimani, researchers have found ceramics and bones from the Proto-Helladic period, more than four thousand years old. From the summit, 750 meters up, the view opens across the whole eastern sea, Skyros and the northern Sporades floating on the horizon.