I visited Attica Zoo in September 2008.
I visited this Zoo last week (December 8, 2011). Arek's excellent review (see above) is still quite accurate. As he said, the Zoo is located in Spata, a small town which is also the hometown of Athens' new (2004) Airport. So it's very quick to get to the Zoo right after landing, which is what I did.
This Zoo has been at the forefront of the political battle with the radical animal rights wingnuts. A year or so ago, the radicals sued the Zoo, because they felt that dolphins should not be kept in captivity. Their (false) claim was that the Zoo brought in wild-caught dolphins, when they are actually from an oceanarium in Latvia. The radicals lost the suit, but they have refused to give up. So now their campaign is to deface ALL of the Zoo's signs giving directions to the Zoo -- which honestly made it very, very hard to find the place! You drive through Spata and see a sign showing directions for 3 places and the 3rd place on the sign is completely blacked out with spray paint! This made me downright mad! Hey idiots, if you don't like Zoos, then don't go to them -- but leave them alone for those of us who love them!
I met both the owner/founder, and I was very impressed with his passion for his Zoo. I'm glad they haven't been discouraged by their radical critics.
Just a few notes to add to Arek's review:
(1) As was noted, there are no more white lions. But the Zoo is justifiably proud of their rather new African lion exhibit. It looks somewhat like the lion exhibit at Florida's Busch Gardens, with a jeep children can climb into, with the front of the jeep being inside the lions' exhibit -- behind glass. There's a tie-in to Disney's The Lion King.
(2) They have what I believe is the best prairie dog exhibit I've ever seen (and I've seen hundreds of them).
(3) Monkey Forest, another European lemur encounter exhibit, is truly impressive.
(4) I was happy to see a European wildcat that was actually moving.
(5) I've never seen so many different birds! Only San Diego comes close!
(6) The children's area was quite nice, with many farm animals, a walk-through petting yard with goats, plus Bunnytown, with 30+ adorable multi-colored rabbits.
(7) By far the highlight was the sprawling Dolphin Stadium, where they give a 30-minute show, 2 to 4 times daily. The first 10 minutes features a funny sea lion. Then, for 20 minutes, they have 14 (count 'em, 14) dolphins performing all kinds of behaviors and some tricks. Loads of fun! They won't always have this many dolphins, as they are only temporarily holding some of them, while their Latvian home is being renovated. Greece is known for its beaches and even for snorkeling and scuba diving, so it's appropriate that they would have a great dolphin show.
Future plans call for the Attica Zoo to add a world-class Aquarium. Before that, they'll open an (already under construction) dinosaur building, with moving animatronic dinosaurs.
. I must admit I prefer zoos keeping purebred Asians or Africans and put their resources in them, but bashing someone for appreciating white lion goes way too far in my view 
