As a rule, they’re about three meters (ten feet) from the ground.
“They” are small mosaics inspired by the Space Invaders video game (circa 1980). They’ve been in Paris for a while, and they turn up in surprising places.
Paris turns out to be the setting for an ambitious street art project by an
artist who calls himself Invader. From the artist’s web site, I learned that installations have been set up in other cities, in France and abroad, as well as at galleries.
There’s also a book about the Paris project.
Finally, Swindle magazine ran a profile of Invader’s work, written by Sheperd Fairey, who considers Invader “one of the most thoughtful and focused artists I’ve ever met”.
“Enjoy a positive mental attitude in a time faced with darkness.”
David Malek wrote that. He’s an American artist, whose work is now on display in Paris, at the southwestern corner of the place de la Madeleine.

Malek’s work isn’t in a gallery; it’s outdoors, where it camouflages a construction site.
The Cerruti boutique is renovating the premises, and chose Malek’s work to cover up what’s going on indoors.
For this moment of art in the heart of the city: thank you Cerruti, and thank you David Malek.

Spotted on the side of a building on the rue Sainte-Croix de la Bretonnerie, at the intersection of the rue des Archives: a stylized image of a roll of toilet paper.
In France, toilet paper is most often pink. Don’t ask me why; it just is.
Here, the artist has whimsically added a pair of hearts, rotating the pair along the roll.
The mirrored initials at the bottom, pq, give the work a title or signature. In French, “pq” is a casual abbreviation for toilet paper.
I can’t say why, but the image stopped me in my tracks.