routes in this corridor are low. The Riverview Corridor is planned to be a LRT/modern streetcar hybrid operating between St. Paul Union Depot and Mall of America. Riverview Corridor trains would share tracks and stations with the Metro Green Line between Central Station and Union Depot Station. Regional rail Numerous existing freight rail lines branch out from St. Paul Union Depot and could be upgraded and utilized by regional passenger trains. Currently MnDOT has studied regional rail from St. Paul Union Depot to Mankato, Northfield, and Minneapolis (continuing further west as a through-service). In 2010, the Minnesota Department of Transportation also released a plan for regional rail stretching out from the Twin Cities to rural Minnesota and neighboring states, and at least some of the lines would run to Saint Paul. High-speed rail New trains running at speeds above to Chicago have also been discussed since at least 1991. The Midwest Regional Rail Initiative (MWRRI), led by the Wisconsin Department of Transportation, has proposed a link to the Twin Cities running at up to . The planned schedule time to Saint Paul would be just 5½ hours. Others including the French national railway SNCF, which operates the TGV network, have proposed trains running at up to . Local significance Prior to the station's reopening in December 2012, Josh Collins, a spokesman for Ramsey County Regional Rail Authority, referred to the potential of the station to be "the living room of Saint Paul." Architecture The entrance to Union Depot, the headhouse, is considered a somewhat severe example of neoclassical architecture, with a robust aesthetic. A series of tall Doric columns line the front façade. The concourse and the waiting room that extends out to the platforms, where trains once rolled in, is considered to be one of the great architectural achievements in the city. Charles Frost designed the station. The waiting room is flooded with natural light from skylights. These skylights were blackened during the Second World War, but restored for the 2012 re-opening. The building was added to the National Register of Historic Places in 1974. The restoration and new addition were designed by Hammel, Green and Abrahamson Architects & Engineers (HGA). Railway mapping Milepost for rail lines that originated in St. Paul, such as the Great Northern and Northern Pacific, had used the depot as milepost 0. This is still evident in timetables and mileposts used by the BNSF