The Edge

 was a Research Facility that the Second Doctor, Jamie McCrimmon and Zoe Heriot once visited. They joined a tour of the facility. Sebastian told the Doctor that the Edge was at the cutting edge of any research you could think of. The asteroid it was on, was made of Acuman, a mind altering drug that Provost Curtis was mining. When Jamie broke the mine's Relative Dimensional Stabiliser it broke apart. (AUDIO: The Edge)