In a residential area in Hendaye, right off a Rue de la Bergerie. It looks like it might be a few feet into a French person's lawn...
Take the 17:45 train from Donostia across the border to Hendaye, and walk to the hash, which according to GoogleMaps is about 25min away. Also planning on purchasing a cherry filled Pastel Vasco at the bakery near Hendaye's main station.
Excited to earn my (LizWiz) third Virgin Graticule Achievement and Krejci's second (in a single month)!!