In the northeastern part of the island, in a location called “Kavos Vasili”, the archaeologists have discovered the ruins of a settlement of the Early Bronze Age. This settlement is the oldest of the wider area of Trizinia, Peloponnese, and is believed to be interrelated with the wreck found on the nearby Dokos island which dates to the same period.
Antiquity Poros was divided into two islands during antiquity: Sphairia (also known by its modern Greek form Sfairia) and
Calauria (also known by its ancient Greek form Kalaureia and its modern Greek form Kalavria). Sphairia consisted of the area of the modern island which includes its current capital. Calauria was the larger part of the island to its north. During the
period of Mycenaean dominance (1400-1100 BC) Calauria was quite powerful and the most important naval base of region was located on islet Monti or Liontari on its eastern coast. The
city-state of Calauria was home to an asylum dedicated to Poseidon, the ruins of which are still accessible on a hilltop close to the town. This asylum may have been linked to the sanctuaries at
Geraistos and
Tainaros. Ancient historians stated that Calauria was the center of an
amphictyony, a religious alliance between its city-state and those of
Athens, Poros,
Aegina,
Epidaurus,
Hermione,
Troezen,
Nauplio,
Orchomenus, and
Prasaiai.
Modern archaeology has discovered no evidence for its actual existence, however, and now believe the "
Calaurian League" to have been a later
Hellenistic invention. An enormous feast was found dating to the Hellenistic period in the ruins of the Calaurian asylum, along with a plaque celebrating the "revival" of its amphictyony. During the 5th century, the
Persian Empire annexed the Greek cities of western
Anatolia. When the Athenians helped these cities in
a revolt against Persian rule, Poros, along with the other Greek states of mainland Greece and the Aegean islands, was drawn into the
Greco-Persian Wars. At the beginning of the
Peloponnesian War, Troezen and Calauria offered asylum to an anti-
Macedonian politician who eventually became the
tyrant of the region. After the death of
Alexander the Great in 323 BC, the
Ptolemies of
Egypt occupied Calauria. Around the same time, the Athenian orator
Demosthenes came to the island, where some report his
suicide. In 273 BC, the last explosion of the Methana volcano dramatically changed the morphology of Poros and the wider region. The Sanctuary of Poseidon has been excavated by Swedish archaeologists. The 1894 field season is considered to be the first Swedish archaeological campaign in Greece. Swedes have continued excavations from 1997 in collaboration with the Greek National Heritage Board.
Roman and Byzantine times During the Roman period (86 BC to 395 AD) Poros was part of the Roman Empire along with Trizina, to which it was a tributary. In
Byzantine times, Poros and other islands were often raided by the pirates that dominated the Aegean Sea.
Venetian period In 1484 the Venetians occupied Poros and used it as a strategic port in their sea battles with the Ottomans. Poros was the most powerful city of the wider area, also governing Methana Island, Epidaurus, Damalas (Trizina), Fanari and Valario. During that time, the island had about 15,000 inhabitants, making it one of the largest cities in Greece.
Arvanites were recorded among the inhabitants of the island in 1688. They lived in poverty as most did in Greece at the time. Venetian rule ended in 1715.
Ottoman period The Ottoman Period began in 1715, much later in Poros than in the rest of Greece. Shipping and commerce were the inhabitants' main activities, but Poros' fleet wasn't as famous as Hydra's or Spetses' fleet, and did not participate in many sea battles.
The Greek Revolution Poros had an important role during the
Greek Revolution in 1821, due to its strategic position. The Greek revolutionary leaders, often met in Poros to discuss and plan their future actions. The first Greek naval base was established in Poros in 1828 and remained there until 1878. In September 1828, the ambassadors of England, France and Russia met in Poros with
Ioannis Kapodistrias in order to determine the borders of the future Greek state, which was established two years later, in 1830.
Russian naval base With the
Treaty of Kuchuk Kainarji,
Russia secured free shipping for its navy, war and merchant alike, throughout the waters of the Ottoman Empire. As Russian naval activity grew, need arose for a supply station, and land was acquired at the edge of Poros town. Extensive materiel,
coal, and food storage facilities were built, as well as a
hardtack baking factory. After Greek independence, Governor
Capodistrias requisitioned the facilities for use of the Greek war navy, and offered the Russians an alternative location in a nearby cove. The new facilities were far larger, and were used by Russian ships throughout the 19th century. The number of Russian residents of Poros increased and even a Russian school was established. Then as Russian naval activity declined, so did the base and by the early 20th century only a single Russian watchman was left guarding it. It was then granted to the Greek Navy by the Czar but was never put to actual use, and the abandoned buildings were left to decay. The ruins, in elaborately carved stone, were listed as protected architectural monuments in 1989.
Twentieth century In the beginning of the 20th century, among the activities of the Poros' inhabitants were agriculture (mainly wheat, grapevines and olives), livestock, fishing and shipping. ==Main sights==