[7][8] Until the 3rd millennium BC, Piraeus was a rocky island connected to the mainland by a low-lying stretch of land that was flooded with sea water most of the year.

In 493 BC, Themistocles initiated the fortifications of Piraeus and later advised the Athenians to take advantage of its natural harbours' strategic potential.

In the following years Themistocles initiated the construction of the port and created the ship sheds (neosoikoi), while the Themistoclean Walls were completed in 471 BC, turning Piraeus into a great military and commercial harbour, which served as the permanent navy base for the mighty Athenian fleet.

In the late 4th century BC Piraeus went into a long period of decline; the harbours were only occasionally used for the Byzantine fleet and the town was mostly deserted throughout the Ottoman occupation of Greece.

In 2002 the Piraeus Port Authority (PPA) and the Greek government signed a concession agreement.

[citation needed] "The port's geographic advantages and the quality services offered by us, have helped deliver rapid progress, in a crisis era" said Fu Chengqiu, managing director of Piraeus Container Terminal in 2012.

In 2014 The Hellenic Republic Asset Development Fund (HRADF), the Greek government's privatization agency, sought to sell a majority stake of the port to finance debt.

[18] In October 2009 Greece leased docks 2 and 3 from PPA to the China Ocean Shipping (Group) Company (in short: COSCO) for a 35-year-period.

According to trade unionists of PPA, the arrival of COSCO led to reductions in salary and social benefits, exclusion of union members and increased pressures on time and performance at the expense of worker safety.

[19] According to an interview in 2012 with Harilaos N. Psaraftis, a professor of maritime transport in Athens, in some cases the salaries of workers were $181,000 a year with overtime before the 20% general pay-cuts imposed on public employees.

Due to union safety rules a team of nine people was required to work a gantry crane.

In 2017 the Athens stock exchange listed company (OLP) almost doubled its pre-tax profits from 11 to 21.2 million euros.

In 2014 the Greek government sought to sell equity of the port as part of an agreement with the EU to recover from debt.

This was met with criticism and resistance by the port's local union as well as a significant part of the Greek population.

[23][24][25] The push to sell the port stalled while the controlling federal political party changed, but that was short lived.

[22] Negotiations between the Greek government and COSCO soon resumed while the resistance to foreign control of the port started to decline.

[22] However, at that point the privatization efforts of the government were inevitable as Greece struggled to raise money to finance debt.

A dockworker, Constantinos Tsourakis, said at the time "This is not a concession, it’s a giveaway of property belonging to the Greek people.

The union Gen. Secretary, Giorgios Gogos, agrees with that assessment, but says the expectation of COSCO to remove the 35/40 percent reduction remains a problem.

He also points out that the 51 percent stake (which will increase to 67 percent in 2021) means that the 100 million dollars that the COSCO subsidiary pays each year to the PPA for use of dock 2 and 3 ends up back in COSCO's hands, not those of the Greek government or people, as originally intended.

[30] Piraeus handled 4.9 million TEUs in 2018, an increase of 19,4% compared with 2017 climbing to the number two position of all Mediterranean ports.

[40] For the 2004 Athens Olympic Games, 13 cruise ships were docked in Piraeus to serve as floating hotels.

Piraeus has been the top cruise destination in Greece for the tenth consecutive year, beating Santorini, Mykonos, Rhodes, and Crete.

Other public buses connect Piraeus with various other areas such as southern coastal zone and central Athens.

[44] For air quality monitoring, the port partnered with the National Technical University of Athens School of Chemical Engineers.

An air quality monitoring station was installed to take measurements of BTEX, CO, NOx, SO2, O3, and PM2.5 and PM10, 24 hours a day.

PPA has also collaborated with the Agricultural University of Athens to enhance the greenery around the port for aesthetic purposes, as well as to remove pollutants from the air.

In 2004 for the Athens Olympic Games, a permanent sewage network was built for the cruise ships that were docked in Piraeus as floating hotels.