In plan, the Hirshorn’s center circular courtyard is not concentric with the outer circle. It actually is off center slightly in the North direction which marks a cross-axis of the Mall, shared by the National Archives building on the north side of the Mall. The axis continues on the other side of the Archives building with 8th Street and the Navy Memorial and National Portrait Gallery (originally the Patent Building built in 1836).
RDCAIA says
In plan, the Hirshorn’s center circular courtyard is not concentric with the outer circle. It actually is off center slightly in the North direction which marks a cross-axis of the Mall, shared by the National Archives building on the north side of the Mall. The axis continues on the other side of the Archives building with 8th Street and the Navy Memorial and National Portrait Gallery (originally the Patent Building built in 1836).