Watching the creation of these flower mosaics is amazing. Designs are prepared in advance and when it's time to start creating the art work, the designs are sketched in chalk onto the pavement. Next soil is used to outline the pictures. Then teams of workers, almost everyone in town, use the prepared flower petals to fill in the designs much like a mosaic. There's someone on hand with a water bottle to spray the flowers to keep them fresh and to keep them from blowing away.
The infiorata originated with the Miracle of Bolsena in 1263 and Bolsena, north of Rome, is still one of the top places to go for Corpus Domini. The flower petal carpet created in Bolsena is about two miles long. Other good places are Genzano di Roma, south of Rome, and Orvieto in Umbria where the historic pageant with about 400 people in costume follows the Corpus Domini procession.
Even going to a small town infiorata is an amazing experience. I watched flower petal mosaics being created in Brugnato, a small town in Liguria inland from Cinque Terre. Here's a video of the Infioriata in Brugnato.