The city of Reims has several hotels near the festival and there are some campsites in the surrounding cities:
https://www.google.fr/maps/search/hotels+reims/@49.2525728,4.0227234,15z?entry=ttu
If you are in a motorhome, you have a parking lot near the International Residence Center (CIS) with 9 spots (5 minutes walk to the Festival):
https://www.grandreims.fr/se-deplacer/les-aires-de-camping-cars-et-campings
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