Tyron

Tyron was a tiny planet in the seventeenth galaxy with "talking stones." The First Doctor, Ian Chesterton, Barbara Wright, and Vicki Pallister had an adventure there before their visit to Palestine in 1190. (PROSE: Doctor Who and the Crusaders)

Ian Chesterton later mentioned the talking stones of Tyron before telling of his adventure in Palestine. (HOMEVID: Ian Chesterton: An Introduction)

In an alternate timeline, the First Doctor explained to Katarina that, although Steven Taylor likely knew little about the talking stones of Tyron, this in itself did not mean Steven was not intelligent. (AUDIO: Daughter of the Gods)