The population of the demos (municipality) of Peiraeus is 175,697 (2001). The nomarchia (prefecture) of Peiraeus, which includes the surrounding land and some of the islands of the Saronic Gulf, has a population of 541,504 (2001). It consists of a rocky promontory, containing three natural harbours, a large one on the north-west which is an important commercial harbour for the eastern Mediterranean Sea, and two smaller ones used for naval purposes.
Themistocles was the first to urge the Athenians to take advantage of these harbours, instead of using the sandy bay of Phaleron. The fortification of Piraeus was begun in 493 BC. In 460 BC it was connected with Athens by the Long Walls. The original town of Piraeus was built by the architect Hippodamus of Miletus, probably in the time of Pericles. The promontory itself consisted of two parts, the hill of Munychia and the projection of Acte. On the opposite side of the harbour was the outwork of Eetioneia.
In 404 BC Munychia was seized by Thrasybulus and the exiles from Phyle, who then defeated the Thirty Tyrants in Athens. The three chief arsenals of Peiraeus were Munychia, Zea and Cantharus, which contained 82, 196 and 94 ships respectively in the 4th century BC.
Some info originally from the 1911 Encyclopedia Britannica.