In Norse mythology, Alfheim, or Ljosalfheimr, is one of the Nine Worlds supported by the World Tree, Yggdrasil. This is the home of the elves (alfar) or light elves (ljosalfar).
In my Vanir Dragon series, the old forests at the edges of the plains are the realm of the magical and mysterious alfkin, ruled over by the Woodland King.
Age-old treaties allow the other races to travel through the forests--but only on established trade routes. Travelers who leave the river or the road are rarely seen again.