During the Peloponnesian War, Piraeus suffered its first setback.
In the second year of the war, the first cases of the Athens plague were recorded in Piraeus.
Consequently, it became the chief harbour of ancient Greece, but declined gradually after the 4th century AD, growing once more in the 19th century, especially after Athens' declaration as the capital of Greece.
In the modern era, Piraeus is a large city, bustling with activity and an integral part of Athens, acting as home to the country's biggest harbour and bearing all the characteristics of a huge marine and commercial-industrial centre.
The port of Piraeus is the chief port in Greece, the largest passenger port in Europe servicing about 20 million passengers annually.