There aren't many places that houses several ecosystems under one roof. The Biodome de Montreal offers a trio of such environments. In some areas, visitors are within a few feet of the wildlife. Being able to physically walk through wall of humidity of the lush jungles, feel the dry air of the deserts and press your face up against floor-to-ceiling tanks offers an experience like kno other.
If you have children, this is hands down a wonderful place to bring them. I can't tell you how many children's faces I saw light up whenever they see an animal for the first time. Even for adults, it's a nice way to spend a few hours. Make sure you look up the schedule to catch the penguin feedings and the educational presentations in their local theater.