Public transport in Athens
Athens is a relatively small capital city, yet has a wide range of transport from trolley, tram, buses and metro that is very modernised with classical music playing on the platforms and some metro stations even having small museums inside with artefacts on display that were dug up during construction.
It's very clean, worth using and easy to use and based around three coloured lines: Blue, Red and Green.
Tickets
The ticket system is easy to use with re-chargable Electronic Cards (paper tickets, so don't get confused and think it should be a plastic card), that you can buy for varying amounts, each allowing a certain amount of journeys. IE: each journey is (only) €1.40 (Athens is not zoned, unlike London) - and you can buy a card, for example, for €13.50 that covers 10 journeys plus one for free.
Machines to buy them have languages in Greek, English, German, French and Russian. So you won't be confused.
Caution: Beware of pick pockets on most public transport – this has been an issue for several years. Do not be distracted or feel sorry for the Roma children who beg and play their music loudly to get money.