Alysos, Rock formation in Kalabaka, Greece.

Alysos is a rock in the Meteora formation complex of Thessaly, overlooking the eastern side of Kalabaka. On it stand the ruins of the Monastery of the Apostle Peter's Chains, probably built around 1400 and known in full as the Monastery of the Veneration of the Chains of the Apostle Peter.

A monastery was built on this rock around 1400 during a period when monks established many communities across the Meteora region. This construction was part of a broader wave of monastic expansion that shaped the area between the 14th and 16th centuries.

The ruined monastery on this rock shows how monks made their lives in this remote place, creating a sacred retreat high above the surrounding land. Visitors today can see where cells and prayer spaces were carved into the rock, revealing daily monastic routines.

Alysos stands above the eastern side of Kalabaka, in the Meteora complex of Thessaly. The sources record no marked trail or climbing route on the rock; the monastery ruins lie on its top and are reached only by unmarked paths. Check local conditions in Kalabaka before setting out, and carry water, as the rock faces are exposed.

Monks developed special building methods to construct the monastery on these steep rock faces, driving wooden supports into the stone and carving space around them. These techniques allowed them to create stable structures in places where conventional construction seemed impossible.