Starting, I think, at the Louvre, there is an invisible line that extends all the way to La Défense.
Things of significance that exist between those two points are built with that line bisecting them.
I always think it's fun to capture images illustrating that phenomenon.
Here is one: it starts at the Ferris wheel, through the Obelisque de Place de la Concord and through l'Arch de Triomphe.
The Grand Arch de la Défense is somewhere in the haze down the line; it sits on the line as well.