It's not true at all. The central arrondissements are (for some part) well preserved, but once you go a little further you'll see that most buildings have been

It's not true at all. The central arrondissements are (for some part) well preserved, but once you go a little further you'll see that most buildings have been destroyed and replaced since the 50s. There are few highrise, but Paris is already very dense and it wouldn't really be able to support these buildings. Since a few years there's a construction boom in and around the city. With the new subway lines to come (greater Paris), new neighborhoods are built everywhere. Your vision of Paris is at least 50 years old...