There must have been hundreds upon hundreds of acres of these beautiful flowering fields between Paris and the Loire. We learned that the plants are called "colza" in French. Or, according to our dictionary, "rape" in English. Of course, "rape" is such an unfortunate name; these days we call it "canola". I had no idea canola was so pretty in the spring! (Actually, before this I had no idea what canola looked like, period.)
Our timing was lucky; a couple of days later, the flowers had definitely faded.