Union Station was the great railway terminus of the Midwest, opened in 1894 and at its peak the busiest passenger station in the world. The Romanesque headhouse with its 65-metre clock tower and the gilded Grand Hall barrel-vault are still spectacular. Passenger trains stopped in 1978; the building was redeveloped as a hotel, festival marketplace, and most recently an aquarium and observation wheel.
The Grand Hall is now the lobby of the St Louis Union Station Hotel and free to walk into. The St Louis Aquarium, opened in 2019, fills the old train shed and is the city's main child-pleasing attraction along with the Ferris wheel out front. The Whispering Arch is one of the architectural curiosities of the building — speak into one corner and a listener at the diagonal corner hears you clearly.