At least in the year 200100, the Great Cobalt Pyramid was a building built on the ruins of the Torchwood Institute. (TV: Bad Wolf [+]Loading...["Bad Wolf (TV story)"])
By 4421, a number of Torchwood's artefacts were hidden beneath the pyramids. Jeremiah Bash Henderson claimed that he and Delilah were planning on getting married there. (AUDIO: The Torchwood Archive [+]Loading...["The Torchwood Archive (audio story)"])
The Cobalt Pyramid was excavated by Bernice Summerfield. She wrote about it, something which was later read by Captain John Hart. (AUDIO: The War Master [+]Loading...["The War Master (audio story)"]).