  Interventions of central, top-down planning are serious limitations to the
possibility of modelling the dynamics of cities. An example is the city of
Paris (France), which during the 19th century experienced large modifications
supervised by a central authority, the `Haussmann period'. In this article, we
report an empirical analysis of more than 200 years (1789-2010) of the
evolution of the street network of Paris. We show that the usual network
measures display a smooth behavior and that the most important quantitative
signatures of central planning is the spatial reorganization of centrality and
the modification of the block shape distribution. Such effects can only be
obtained by structural modifications at a large-scale level, with the creation
of new roads not constrained by the existing geometry. The evolution of a city
thus seems to result from the superimposition of continuous, local growth
processes and punctual changes operating at large spatial scales.
