After bidding adieu to La Tourette, we high-tailed it to nearby Firminy, south of Lyon, to gawk at several Le Corbusiers.
Saint Pierre is another one of those projects deemed "Corbu's last project." This one feels real since it started in 1970, some five years after his death, and wasn't finished until 2006 (!!!), 41 years after his death. Construction stopped in 1978 with a rough foundation of the church built:
by Peter Christian Riemann - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=147159598
Controversially, the foundations above were given historic monument status in 1983, a decree that saved the church.
Finally, construction restarted in 2004 under the supervision of a Corbu student, José R. Oubrerie, who worked with Corbusier on the original design. The church was finished in 2006.
Corbusier mined his unrealized projects for this church, borrowing from a 1929 design for Le Tremblay:

source: https://www.fondationlecorbusier.fr/oeuvre-architecture/projets-eglise-le-tremblay-le-tremblay-france-1929/
The church is simply stellar. Located on the approach to an array of Corbusier buildings (and soccer field!), it perches high, massive, and abstract. Entry is around the back where we noticed that the arches and lines along the exterior are for managing rainfall runoff: stylized concrete gutters. They appear abstract but are completely functional.
Entry in the back is to human-scaled rooms. The chamber, which explodes above you, is up a flight of stairs. Similar to La Tourette, Corbu used indirect light and painted concrete to carry color into the dark space. Direct light is carried into the space through small circular holes seemingly shotgunned into the building, an intent of the architect. Light cannons quietly fire above in red, yellow, and blue.
The space is truly magical. For a nominal ticket price, you are allowed to wander, sit, and enjoy as long as you want. It would be wonderful to have stayed long enough for a service (although not officially sanctified, the church is noted to be Roman Catholic). This is the Modernist, minimalist answer to cathedrals, and it filled us with the same awe. The starkness is perhaps more appropriate, discrete beacons of light emitting from cold, gray concrete.