As one of the only (if not only) zoos in North America to divide its animals up by region rather than species, the Toronto Zoo is quite unique. Each zoogeographic region (Indo-Malaya, Africa, the Americas, Australasia, Eurasia and the Canadian Domain) has both an indoor and outdoor exhibit - except for the Canadian domain.
While the zoo covers a lot of space (710 acres) and therefore requires a lot of walking, it does have a zoo-mobile which you can buy tickets for and then catch and use all day.
There are over 5000 animals at the zoo, one of the largest in the world. Well worth a visit. If you live in the area it is worth buying a pass for a year as daily tickets can be quite steep.
There is plenty of food available, but if you prefer to bring in your own there are a lot of picnic tables throughout the zoo.
Some must see exhibits include African Savanna, New Great Barrier Reef, and the award-winning Gorilla Rainforest.