There is no outdoor pool and the small yard that you can see in the photo is the entire outdoor area for the two hippos. However, the underwater viewing is spectacular for visitors and a very popular part of the zoo. Nile Hippo exhibits without underwater viewing cannot even compare in terms of a visitor perspective and sadly only about a dozen zoos in all of North America have such a setup. Calgary advertise on their website that they have "North America's largest indoor hippo tank" although that might not be saying much as most of the underwater viewing exhibits for hippos are set outside. Three times in the past week, while on holiday in Calgary, I've taken my family to the Calgary Zoo and on two occasions we've hit the African Savanna building early in the day and watched from very close proximity while the two hippos ate their morning breakfast. Then they each plunge into their pool and it is an awesome sight to see. After that there is a toilet break (tremendously exciting for young kids to see hippos poop) before they head outside to bask in the sunshine.