When Pierre Charles L'Enfant was designing the city of DC, he wanted it to intimidate the leaders of Europe.
Also, large roundabouts were built to confuse invading armies and direct them away from the White House and Capitol Building.
Apparently the British were not fooled at all when they came and burned down the city in 1812, BUT we are now blessed with massive traffic circles such as Dupont Circle, Logan Circle, and Washington Circle (to name a few).
I would like Mr. L'Enfant to know that despite his poor planning, I can officially say I have mastered driving in DC and am now competent enough to get to all major destinations within the District. No small feat if you ask me.