Paris - Ile de la Cité pre-1850's

I've been reading about Haussmann and the modifications he made to Paris in the 1850's, helping to make Paris into the beautiful city it is, with broad avenues, public parks, etc.  But when the book explained about how many people he displaced, I had a hard time imagining... Came across this map of Paris in the Carnavalet museum.  This shows the place in front of Notre Dame, and the bridge crossing into the Latin Quarter - all chock-a-block full of houses!  And all of Paris was like that, making it a dark, dirty, and dangerous city.  That kind of urbanization could only take place under an autocratic Emperor (or monarch) : this was Napoleon III's vision of restoring Paris to its glory in Europe!