The building sits on a raised "island" of sorts between two open trenches, one for the Jones Falls Expressway and the other the tracks of the Northeast Corridor (NEC). The NEC approaches from the south through the two-track, 7,660-foot Baltimore and Potomac Tunnel, which opened in 1873 and whose 30 mph limit, sharp curves, and steep grades make it one of the NEC's worst bottlenecks. The NEC's northern approach is the 1873 Union Tunnel, which has one single-track bore and one double-track bore.