Why does the track between Smithsonian and Federal Triangle curve around? Couldn't it have gone straight down 12th St?[/i]
It curves to the west to pass around the 12th Street tunnel under the mall. The tunnel was built before WMATA began building the D Route. The entire segment from the vent shaft structure at the north end of the Federal Triangle station to the transition to bored tunnels east of 12th and C Streets SW was built using the cut and cover method. The elevation of the mezzanines in Smithsonian station are roughly at the same elevation as the roadway in the tunnel under the mall.
John in the sand box of Maryland's eastern shore.