I was skeptical about spending the whole day on a ...

I was skeptical about spending the whole day on a trip to the zoo, but it's completely worth it. They have a wide range of animals, which are kept in enclosures resembling their natural habitats as opposed to cages. The zoo also runs a lot of wildlife conservation projects and runs as a nonprofit so every $ you spend goes back to the animals.
The basic ticket gets you a busride and a skyride, make sure to grab a map and get the busride first so you get an overview of what animals are located where and to plan your walk later(the zoo is huge). There are several cafes and gift shops throughout.