I agree with almost all the previous comments. Colchester has a very big collection and you need a full day (or preferably two full days) to stand a hope of seeing everything. Bear in mind though that Colchester does, very sensibly, open slightly earlier than most UK collections at either 9 O'clock or 9.30 (I can't quite remember). There is too much fake rock and, I agree, the Pygmy Hippo enclosure and Patas Monkey enclosure are rather poor, and the hornbill aviaries are quite low. But these are niggling complaints. It concentrates on ABC animals, and has most of the megafauna that you would once have expected to find at London Zoo (though it doesn't have gorillas). But it also has enough rarer, lesser-known or seldom-exhibited species to appeal to the true zoo enthusiasts who are bored with seeing meerkats and short-clawed otters everywhere (though it has these too). How about these:sun bear, two species of anaconda, tamandua, bearded saki monkey, Geoffroy's cat, buffy-headed capuchin, cherry-crowned mangabey, binturong, gelada, black-backed jackal (need to take the roadtrain to see the latter), Turkish spiny mouse, spotted hyena, mandrill, aardvark, smooth-coated otter, Visayan warty pig (believe they're still there, though didn't see them on my last visit), Philippine spotted deer, African hunting dog, Komodo dragon, Cuban and slender-snouted crocodiles, Amur leopard, giant anteater. I could go on and on. Most of the birds are big, impressive species that appeal to visitors: hornbills, vultures, condors, ostriches, flamingos, cranes, etc., and of course penguins (in two locations). I should also0 add that Colchester probably has more talks, demonstrations and feeding displays than any other zoo, but of course if you choose to go to any of these, you will find you have even less time just for wandering around. Anyway, enjoy.