St. Louis union station is a national historic landmark train station in St. Louis Missouri. St Louis Union Station, once the world's largest and busiest passenger rail terminal, spans 11 acres, beginning from its 65-foot barrel, vaulted ceiling in the Grand Hall to its Victorian-engineered train shed. It was opened to the public in 1894 but ceased operation as an active train terminal in 1978, with reconstruction in the early 1980s as the largest adaptive reuse project in the United States. It houses a 539-room Hyatt Regency Hotel, luxury offices, four active train tracks, and a plaza for festivals, concerts, and other special events. 

The final passenger train departed on October 31, 1978, at 11:38 pm, closing the first chapter in the station’s history. While St. Louis station was reopened as a mixed-use complex featuring retail shops, event spaces, and restaurants where tourists and locals alike could come and spend the day enjoying downtown St. Louis. Today, Union Station is a balance of nostalgia and renovation with the addition of the aquarium which was opened to the public on December 25, 2019.