A river in Europe that Wolfram von Eschenbach says was named after Perceval’s grandfather Gandin.
The river Wolfram revers to is likely the Grajena River (Gradaščica River in Slovene), which is a tributary of the larger Drava River (Drau), and its course includes areas near the medieval Borl Castle.
Source
Parzival | Wolfram von Eschenbach, 1200–1210