I recently watched a TV program related to the renovation of Paris. l like Paris very much and I have been there many times in 2013, 2015 and 2019, but I did not even think that the streetscape in Paris underwent a great change in the middle of 19th century. I am afraid this is like teaching a fish to swim for a person familiar with the history of Paris, but I just made a note as follows:
Paris was rebuilt due to the dysfunction of the sewage system. In the 19th century, Paris was becoming more urbanized due to the influence of the Industrial revolution. However, urban functions in Paris could not keep up with the rapid population growth, and there were still narrow alleys all over Paris in those days. Besides, residents threw excrement away from windows into alleys, so the town had poor sanitation conditions and cholera was spreading there.
Napoléon III appointed Georges-Eugène Haussmann as a prefect of Seine. Haussmann supervised the project of renovation of Paris around 1852. First, 20,000 buildings were demolished for the redevelopment. Wide straight streets were built on the ruins of the old buildings. Trees were planted along the road. This kind of street is called a boulevard. Moreover, the height of the building and the decoration of the facade were also restricted. As a result, the city became a unified beautiful landscape.