Sanctuary Base 6 was a huge base staffed with humans and Ood on Krop Tor.

Sanctuary Base 6 was built by the Walker Expedition. The scientists involved were studying K37 Gem 5, a black hole and the power source keeping Krop Tor from getting sucked in. The base was destroyed when the planet it was on was consumed by the black hole. (TV: The Impossible Planet / The Satan Pit)

The Tenth Doctor kept his Sanctuary Base 6 space suit in the TARDIS. He wore it to stroll on the surface of Mars. The helmet was damaged in the escape from Bowie Base One and abandoned shortly after. (TV: The Waters of Mars) The Eleventh Doctor had replaced the helmet by the time he wore the suit on primordial Earth. (TV: Hide)