Chattanooga sits on the Tennessee River in southeast Tennessee, a mountain city of bridges, trains, and riverfront parks. Lookout Mountain rises above the city, reached by the Incline Railway, and Ruby Falls drops through a cave deep inside the mountain. The Walnut Street Bridge, one of the longest pedestrian bridges in the world, spans the river to the NorthShore shops and restaurants. The Tennessee Aquarium, on the riverfront, shows river life from the mountains to the Gulf, and the Chattanooga Choo Choo, a former train station, still anchors the south side of downtown.