Any apartment building in Japan is called a “mansion”. I was rather confused the first time my friend mentioned he lived in a mansion since he didn’t seem to be a rich person. Of course, there are many luxurious “courts” of apartment buildings, but they don’t have doormen, and most of the time they are actually rather conventional-looking.
The added value is in the name, an instant upgrade with a random foreign word makes it sound more fancy, like “Eclaire”, or “snowy morning”.
As I am learning Japanese it is a good practice to read the katakana alphabet that is used to spell foreign names.
An obligatory arch (a simple metal beam) completes the entrance to “La Rivière” (the only waves nearby are the endless trucks on Kanana-dori).