Taxis operate a 24-hour service and are quite cheap. They can be hailed down on the street or otherwise picked up at taxi stands around major tourist squares such as Monastiraki and Syntagma. You can also book one calling the radio taxi line. Most taxi drivers speak English, however you will come across some who don't.
Are taxis easy in Athens?
The average taxi ride costs between 4EUR and € 6 ( US$ 6.50). In other words, a taxi to get around the city center costs a little more than two metro tickets. Taxis are very easy to flag down, since there are over 12,000 vehicles in the city.