Skull Valley (Ryūga Dani; lit. "Valley of Dragons") is a location just outside of Mount Paozu which was seen in the second episode of Dragon Ball, "The Emperor's Quest" and in Chapter 2 of the Dragon Ball manga. Skull Valley was named only in the anime.
Goku and Bulma camp out there for the night on the first day of their journey to collect the Dragon Balls. The land is very normal, but another part of it is a canyon full of bones and populated with carnivorous wolves. Emperor Pilaf's minions Shu and Mai investigated a glow coming from the valley thinking it was a Dragon Ball. The scenes of the wolves and bones are only part of the anime.
Turtle was also found around here by Goku and Bulma to take to the beach. In "The Nimbus Cloud of Roshi", the place was shown again in a small scene of Bulma taking the Capsule House back with her to continue the journey.
In the Credits scene for most of Dragon Ball, Skull Valley is shown along with the Capsule House on a rainy night with Bulma looking out the window in her night gown.
An unnamed location in the video game Dragon Ball Z: The Legacy of Goku is likely to be Skull Valley. It is right outside of Mount Paozu, and is filled with wolves and bones.