The Eads Bridge crossed the Mississippi River on the northern edge of downtown St. Louis with wagons / street cars on the upper level and two railroad lines on the lower level. The railroad lead to two single bore tunnels (rock walled) that curved to the south to open up just east of St. Louis Union Station. As I recall the tunnels were abandoned in the early 1970's due to clearance issues on the bridge and traffic was rerouted over the parallel McArthur Bridge. I toured one of the bores in the mid 1970's and found partial flooding and at least one concrete pier from an overhead building piercing the tunnel. Not too long afterwards Bi-State/MetroLink refurbished the tunnels for light rail service digging out a section for the 8th and Pine Stations. Re-using old infrastructure can make sense!