Before it was a harbour, Piraeus was almost an island. In prehistoric times, a low-lying land bridge connected the rocky outcropping to the Attic mainland, but the passage flooded most of the year and was used as a salt field — its ancient name, the Halipedon, means precisely that. Over centuries the land silted and rose; the flooding stopped; by early Classical times the peninsula could be crossed safely year-round. The geography proved exceptional: three natural deep-water harbours on a rocky headland. The main harbour, Cantharus, handled the commercial fleet. The two smaller ones, Zea and Munichia, served the warships. In 511 BC, the hill of Munichia was fortified by the tyrant Hippias; four years later Piraeus was formally made a deme of Athens by Cleisthenes. Themistocles saw the strategic potential and acted on it. With silver from the mines at Laurion — a new vein discovered in 483 BC and applied to shipbuilding — the Athenians funded a fleet of 200 triremes. Piraeus became the arsenal of the Aegean. In 399, even amid post-war economic disruption, the city was still collecting 1,800 talents in harbour dues.

Power carries enemies. In 404 BC, the Spartan fleet under Lysander blockaded Piraeus and Athens surrendered. The Long Walls were torn down. The fleet was surrendered. The shipsheds pulled apart. What had taken fifty years to build was demolished in a season. Recovery began but never fully arrived before the next blow: Sulla captured and totally destroyed Piraeus in 86 BC. The Goths under Alaric completed the destruction in 395 AD. For the next fifteen centuries, Piraeus barely existed. The Venetians called it 'the port of Sithines' — a corruption of Athens, the city it served — and in the 14th century the harbour gained its medieval name: Porto Leone, after a colossal ancient lion statue that stood at the harbour entrance. The Ottomans took the port in 1456 and called it Aslan Liman — 'Lion Harbour,' a translation of the Venetian name. They, too, found little use for it. The lion itself was looted in 1687 by the Venetian admiral Francesco Morosini during the Morean War and carried to the Venetian Arsenal, where a copy stands at the harbour entrance today. Under Ottoman rule, Piraeus was mostly a customs house and a monastery. Its population when Athens became the capital of the modern Greek state in 1832 numbered around 300 people — fishermen, largely — in a place that had once housed tens of thousands.

After Greek independence and the designation of Athens as capital in 1832, Piraeus began its second growth. The Athens-Piraeus Railway opened in 1869 — the first railway line in Greece. The Corinth Canal was completed in 1893, making Piraeus more strategically central than ever. New quays, dry docks, and commercial buildings rose along the waterfront. By the end of the 19th century, the population had reached 51,020. Then came the decisive years of 1912 to 1922. The Balkan Wars and then the First World War left Greece exhausted and its borders disputed. The catastrophe that ended the Greek military campaign in Anatolia — the Greco-Turkish War of 1919–1922 — was followed by the Convention on the Exchange of Populations: 1.2 million Orthodox Christians from Turkey and 400,000 Muslims from Greece were compelled to leave their homes and cross to the other country. Hundreds of thousands of Greek refugees from Asia Minor arrived at Piraeus. Many had lost everything — property, community, the graves of their parents. The population of Piraeus nearly doubled in eight years, from 133,482 in 1920 to 251,659 in 1928. They settled in the suburbs: Nikaia, Keratsini, Perama, Drapetsona, Korydallos. With them came the music they had brought from Smyrna and Constantinople — rebetiko, the blues of the dispossessed — which found its most fertile ground in the port cities of Greece.

After the Second World War — during which German forces used the port and the rail line for military traffic, and resistance groups damaged the infrastructure in retaliation — Piraeus rebuilt slowly. The post-1955 recovery reshaped the city. Then came another transformation: the post-2008 financial crisis opened the door to foreign ownership. China Ocean Shipping Company (COSCO), a Chinese state-owned enterprise, gradually acquired the port. Container traffic rose from 400,000 TEUs in 2008 to nearly five million in 2018. Piraeus is now among the ten busiest ports in Europe by container volume and the leading container port in the Eastern Mediterranean. The central harbour serves ferry routes to Crete, the Cyclades, the Dodecanese, and the northern Aegean; the western section handles cargo. On summer evenings the ferry terminal is one of the most vivid places in Greece: enormous ships manoeuvring in the dark, families dragging suitcases over cobblestones, the smell of diesel and sea-air mixed, the sound of announcements in three languages.

Piraeus is not only a port; it is a city of 168,151 people (2021 census), the fourth-largest municipality in Greece. It has its own cultural life, its own football team — Olympiacos F.C., the most successful club in Greek football history, whose home is the Karaiskakis Stadium in Neo Faliro — and its own neighbourhoods with distinct characters. The hill of Kastella, crowned with neoclassical mansions and the open-air Veakeio Theater, looks out over Athens and the Saronic Gulf. Mikrolimano, the smallest of the three ancient harbours, is now lined with fish restaurants and sailing boats. The Municipal Theatre, built in 1885 and still standing, is one of the finest examples of neoclassical architecture in the greater Athens area. Four bronze statues discovered underground near the Tinaneios Gardens in 1959 — an Archaic Apollo, a large Artemis, a smaller Artemis, and an Athena — are now the centrepiece of the Archaeological Museum of Piraeus: masterworks of ancient bronze-casting that had been hidden, perhaps for safekeeping, and lay in the earth for roughly two thousand years before a construction crew hit the hand of the Apollo with a drill.