I have a hard time with zoos. What's so great about the one in Amsterdam?
I'm not normally massively into them myself, but it's really big and thoughtfully laid out and they've got all the really classic 'charismatic megafauna' (your lions, elephants, gorillas, parrots etc.) as well as some less obvious animals - fascinating tiny mammals, amazing beetles, fish, octopuses, all sorts. I like really snails so I enjoyed the snailarium a lot. For a lot of them you can ambiently wander around among them. This is especially neat in the case of the tropical butterflies - actually that chamber also contains some small, very brightly-coloured frogs, which I guessed (it turns out correctly) to be poison-arrow frogs. How that got OK'd on health and safety grounds, I'll never know.
The performing sealions are just next level, they have to be seen.
Only downside is that it's a bit sad seeing obviously intelligent creatures kept in enclosures that would normally have a huge range, but on the flipside, at least at the zoo they're not in danger from fucking poachers or bushmeat hunters or whatever.
Oh and there's a special museum of microbes next door that's also managed by the zoo, so you can make a saving by buying tickets for both attractions. We spent a good half a day there and there were still some animals we didn't see.