The Aquarium in downtown Houston is an aquarium with 500,000 gallons of water. It has more than 200 species of aquatic organisms of different shapes and sizes from all over the world. Indoors include tropical rainforest series, ancient Maya Civilization Exhibition halls, etc. Outdoor attractions include a 100-foot-high Ferris wheel overlooking downtown Houston, a variety of underwater biological ornaments, and a mini train to take you on a tour of underwater tunnel sharks.