Planned cities like Washington D.C. were designed explicitly to prevent the kind of barricade street warfare which broke out in Paris and allowed the French Revolution to take place. Try building a barricade around Congress. You can't do it. It's placed in the middle of a vast open space for a very specific reason. Large swaths of Paris were later demolished and replaced with wide open boulevards under the reign of Louis Napoleon for the same reason. These cities are designed so that if you want to get a column of mounted troops to the center to break up demonstrations, you've got no less than 6 or 8 choices of massive roads to approach from.