In 1852, Napoleon III commissioned Haussmann to modernize Paris by building safer streets, large avenues connected to the new train stations, central or symbolic squares (such as the famous place de l’Etoile, place de la Nation and place du Panthéon), improving the traffic flow and, last but not least, the circulation of army troops. Haussmann also built modern housing with uniform building heights, new water supply and sewer systems, new bridges, etc (see Fig. \[fig:map\_H\] where we show how dramatic the impact of Haussmann transformations are).

The case of Paris under Haussmann provides an interesting example where changes due to central planning are very important and where a naive modelling is bound to fail. We analyze here in detail the effect of these planned transformations on the street network. By introducing physical quantitative measures associated with this network, we are able to compare the effect of the Hausmann transformation of the city with its ‘natural’ evolution over other periods.

By digitizing historical maps (for details on the sources used to construct the maps, see the Methods section) into a Geographical Information System (GIS) environment, we reconstruct the detailed road system (including minor streets) at six different moments in time, $t=1,2,\ldots,6$, 