Piraeus is located in the south of Greece and at the estuary of the Aegean Sea. The city faces Saronic Gulf and is only more than 10 kilometers away from Athens. It is the third largest city in Greece, behind Athens and Thessaloniki, with a population of 180,000. At the beginning of the last century, it was referred to as the Manchester of the East. Now the city is the largest port city and shipping center of the Mediterranean and a commercial and transshipment hub in Greece and the surrounding areas.

The governments of Shanghai and Piraeus signed an agreement of sister-city relationship on 24 June 1985.