Zaragoza Aquarium is the largest freshwater aquarium in Europe. It has a huge freshwater tank with 2 million litres of water and a depth of 9 metres. In the aquarium you can learn about the river systems around the world, with one for each continent: Nile (Africa), Mekong (Asia), Amazon (the Americas), Murray-Darling (Oceania) and Ebro (Europe). Although the vast majority of animal species exhibited are fish, you can also see some vertebrates such as reptiles (alligators, snakes, turtles and lizards, etc.), mammals (otter, marmoset), and amphibians (frogs). A great place to visit, really fascinating.
Inside the Monasterio de Piedra, you can enjoy an entertaining spectacle of birds of prey (check timetable upon entry). You can also visit the birds after the shows. I advise you to bring snacks or to eat before going in, because once you enter the park, you can not leave and re-enter.