Piraeus is the ancient port of Athens and still functions as the chief exit point from the city by sea for destinations amongst the Aegean Islands and elsewhere in the east Mediterranean. Domestic destinations include all of the Aegean islands except the Sporades and some smaller Cyclades and Dodecanese isles that require a connection. International destinations (apart from cruise ships) include Cyprus and the Middle East.
The Port of Piraeus occupies a huge territory. Check your gate number  in advance so you know where to go (it may take 15 minutes of driving / 30 minutes of walking to reach one end of the port from the other).
Since privatisation of the Port of Piraeus Authority  passenger facilities have improved greatly. Air conditioned tents have been set up at departure locations around the port and free wi-fi internet access is now available.
Sailings (arrivals and departures) are posted outside the Coast Guard Building at Karaiskaki Square, the main bus terminal for the Piraeus suburbs. Sailings are also available online for cruise ships or from the Ministry of Merchant Marine .
The area can become hectic, especially during the summer period, so allow plenty of time to navigate to the correct departure gate.
Most travellers arriving in Piraeus from central Athens make use of the very convenient Metro . Line 1 terminates at the Port, from there it's a short walk to the Saronic Gulf ferries, hydrofoils and catamarans, or a free shuttle-bus ride to the ships sailing to Crete and the Dodecanses. Central Cyclades ferries conveniently sail from just across the metro station. Metro ticket costs €1.40 and allows unlimited connections on all modes of transport within 90 minutes.
Direct Airport Express buses  run 24 hours between the port of Piraeus and Athens International Airport . Allow 90 minutes for the trip. Bus tickets to the airport, available from the driver, €5. The Airport is also accessible via the Metro, with a connection at Monastiraki. Metro tickets to the airport are €8.
Other public buses connect Piraeus with its outlying suburbs, the southern coastal zone and with central Athens. Bus and trolley-bus tickets cost €1.40 and are valid for unlimited connections(including metro) within 90 minutes. They must be bought in advance (generally from kiosks or inside metro stations) and validated once on board.
By cruise ship
During the "summer season", a large number of cruise ships call on the port of Piraeus. Modest-sized ships dock near Gate E11, within easy walk of the Cruise Terminal A (Miaoulis). Large ships dock about 400 meters farther away near Gate E12, closer to the busy entrance to this harbor. In June 2013, a newly expanded Cruise Terminal B (Themistocles) opened near Gate E12. The two terminals can handle up to 25,000 passengers per day. When Terminal B is closed, and all passenger facilities are handled by Terminal A, a shuttle bus links the ship(s) docked at Terminal B to Terminal A.
From the Cruise Terminal, which is approximately a mile south of the Metro station, you could take a taxi (about € 9 one way to the Metro station), or you might find a city bus N° 859, 843 or 826 at Miaoulis avenue at the Apheteria bus stop in between E11 and E12. They all make a stop at the metro station (Stathmos ISAP). Buy a combined ticket (bus, metro subway) from € 1.40 per person (valid until 90 minutes after validation) and validate it when on board. Otherwise, you face a 20-minute walk with gates to ferry and freight docks on the shore side, and various commercial and civic buildings on the other side of the very busy Miaoulis Avenue. Stay on the harbor side of the road, and pass several gates all starting with the letter 'E'. The Metro Station (a yellow neoclassical building with white trim) is opposite gate E6 and is accessible by the (only) pedestrian bridge over the busy port road. From here, Metro Line 1 (green) links Piraeus with downtown Athens' Monastiraki station in 20 minutes; train departs every 10 minutes between 6:00 and 24:00.
The centre of Piraeus and the Port can be negoatiated easily on foot if you are not carrying luggage. Yellow trolley buses (trolley bus no 20) are useful for the run from the Port to Passalimani and then follow the very scenic route around the hill of Castella, terminating at the Line 1 Metro station of Neon Phaleron (Neo Faliro), near the Peace & Friendship and Karaiskaki Stadiums.
Free shuttle buses inside the Port run from across the Metro Line 1 Terminal Station, around the north side of the port to the ships sailing for Crete, the Eastern Aegean and the Dodecanese.
Public bus #843 runs from the Apheteria bus stop between the two cruise terminals to the Line 1 Metro station ISAP/Stathmos and beyond.
The most important thing to do is to take a ferry to the Greek Islands. You also can have a nice walk in the Pasalimani/Mikrolimano area and look at many amazing yachts and ships. Or walk from Pasalimani up on the hill of Kastella, where you have amazing view over Athens, the harbour and the saronic gulf.
Another major option is to take the Metro to various parts of Athens (see map of routes on main Athens page). Cost is very modest, and service is very frequent.
If you are feeling lazy, Piraeus does have a beach, albeit not a spectacular one. Taking a stroll down the marina can also be very relaxing.
There isn't much to buy in Piraeus. Wait until you get to your destination to begin purchasing souvenirs. However, there are many shops and cafes along the harbor front, especially toward the cruise terminal from and near the Metro station.
Piraeus justifiably has a higher concentration of food stands than other Greek cities, selling snacks, sweets and best of all, koulouri (Greek: κουλούρι), at prices below 1 Euro.
Good cafes are very scarce in the port.
Piraeus is a rather chaotic place with traffic that's horrendous even for Greece. Particular caution should be used when crossing the street, or when walking along the pavement by the ferry quays where cars, taxis, and trucks often drive randomly among the crowds of travelers walking to and from the boats.
Piraeus is a huge port filled with sailors, and parts of it are about as tough as you'd expect such a place to be. The areas right by the ferry quays are safe enough, but avoid wandering around the rest of Piraeus, especially at night, unless you know your way around.
Unlicensed taxi drivers often meet arriving ferries. Unlike in some countries, these taxis have a bad reputation and should not be considered as a cheap alternative to licensed cabs.
Pickpocketing gangs have been reported working on the Piraeus-Airport bus; for a full description see the Athens Stay Safe section.
One scam you may encounter in Piraeus is a rather subtle one. A man will walk up to you while you are waiting with your luggage in line to board a ferry. This gentleman is a consummate actor: though he doesn't actually claim to be working for the boat or port, his demeanor and behavior imply strongly that he is. He'll pick up your luggage, brushing aside any objections, and usher you with it to the head of the line, at which point he'll demand a hefty tip. In one reported case the bite was €7.00 (our respondent decided the performance was worth €2.00)