In the film "The American President," Sydney Wade describes getting stuck on this roadway, saying she can never remember which lane to take. She also claims to have encountered it on the way from Capitol Hill to the White House, which... no. What NW roundabout - located northwest of both the White House and Capitol Hill - sits along Massachusetts Avenue's Embassy Row at the intersection of 19th and P streets (as well as two other state avenues)?
DUPONT CIRCLE