Housing more than 12,000 species of fish, reptiles, amphibians, birds and mammals on four levels, the aquarium's major exhibits trace the course of the Tennessee River from its origins in the Smoky Mountains to its merger with the Mississippi River and ultimate destination in the Gulf of Mexico. The Penguins' Rock exhibit chronicles two cold-climate species of this well-loved water bird, while the nearby IMAX 3D theater offers deep-sea themed film features.