During the revolution, no one had an accurate map of Paris.<p>This is what made the barricade such an effective tool.  People could throw up a few barricades and quite effectively defend a neighbourhood.<p>When the army showed up they had to channel through narrow unfamiliar streets.<p>If the tide turned against the people, they often managed to escape through a little known back alley.<p>The &quot;Grande Boulevards&quot; may look majestic, but they are also military roads.  They make it easier to move troops within the city.