Well, we only drove past it eight times, but we finally turned off the road to visit the Château d'Avignon.
The first time we drove past the sign, we were surprised - we were nowhere near the city of Avignon! It turns out that this is the estate of the family of Avignon (and nothing to do with the city). From the flyer:
"Set on the western edge of the Rhône delta, the Château d'Avignon is an unexpected combination of green landscapes, technology and architecture, created by the innovative mind of Louis Prat-Noilly.
In 1893, this rich merchant from Marseille purchased a château built in the 18th century by the Avignon family. The innovative mind of the new owner contributed to a radical transformation of the former country house, which became a beautiful hunting pavilion as a result of his initiative. ... The technological discoveries introduced at the universal expositions of 1889 and 1900 are here along with the devices that resulted from the theories of that time about sanitation and luxurious decors which reveal his upper class tastes."
This is the outside of the château - we toured* the inside, but photographs were prohibited. There were certainly a lot of luxurious bedroom suites, bathtubs with hot running water, electricity, systems for using the kitchen to heat and pipe water to various parts of the house.
The owner had spent considerable effort on exotic plants for the grounds - we saw yucca, magnolias, palms, and many plants we recognized from the Americas. These magnificent trees lined the drive.
There were a number of outbuildings, including a "heating building." It contains a coal boiler that heated water for the château (and it was a good 50 yards from the château - imagine the wait!). It also contained a car garage and mechanic's shop.
These are a forge and factory, and part of the water treatment system
This had a perfect floor for dancing :-)
We figured it wasn't quite the Pont d'Avignon, but close enough for us!
This water tower filtered sediment from the water and provided hydrolic power for electricity.
*while visiting the grounds was free, going inside the château was 4€ each. We aren't big fans of audio guides, so we declined them here. Well, it turns out there aren't any other explanations (no written descriptions), just some titles of the various rooms.