Ryos was a planet generally ignored by space travellers and dismissed as an ugly wasteland.
Its geology was distinguished by massive hoodoos which were connected to each other through narrow natural stone bridges. Native species included the Ryosians who lived on the high plateaus and a large domesticated beast of burden. Ryosians built thatch huts, indicating the presence of some kind of grass or rush.
In the 82nd century, a medic crashed on the planet and both the Seventh Doctor and Keepsake came in answer to her distress signal. (Keepsake)