Actually, it’s called the Attiko Parko, the Zoological Part of Attika, but anyway, who is fooled ? It’s the zoo of Athens :) If you want to go there by bus or metro, be careful : you need to go to the station Doukissis Plakentia (the line of the airport), then take the bus 319, until the townhall of Spata, and after the 320. When you’re in the 320, be extra careful because there is actually very very signs indicating the zoo itself. Ask the driver.
This is actually quite a nice place, with a wide range of animals to see, from the birds to the reptiles, through the big cats, and of course, the common poultry and rabbits let loose in the paths of the zoo. Here are some specimens.
Entrance : 15 euros.