Pyramid

A pyramid was a three-dimensional structure composed of three or four sides composed of (usually) triangular shapes.

The great pyramids of Egypt of Earth were well known to other races.

One splinter of Scaroth caused the pyramids to be built. (TV: City of Death) The Osirians also influenced the building of the pyramids, and other pyramids were definitely constructed by 'aliens'. (TV: Pyramids of Mars, PROSE: Dead Romance)

Khepren supervised the construction of a pyramid. (TV: The Daleks' Master Plan)

The Exxilons influenced not only the Egyptian, but also the Aztec pyramids during their visits to Earth. (PROSE: The Left-Handed Hummingbird)

Anubian spacecraft had a pyramid shape. (TV: Curse of Anubis)

In a timeline where all of history was happening at once, Area 52 was housed inside a pyramid. (TV: The Wedding of River Song)

Minor References

 * The Great Intelligence used a three-sided pyramid constructed from Yeti control spheres as its physical form, though it truly had no physical form. (TV: The Abominable Snowmen)
 * When showing Adric the chameleon circuit of his TARDIS, the Fourth Doctor demonstrated that he could disguise the TARDIS as a pyramid, including a door so they could get in and out. (TV: Logopolis)
 * The Rani's TARDIS on Lakertya was disguised as a pink pyramid. (TV: Time and the Rani)
 * The Eleventh Doctor took Kazran Sardick and Abigail Pettigrew to visit the pyramids of Egypt on one of the Christmases he and Kazran visited Abigail. (TV: A Christmas Carol)
 * Sarah Jane Smith sabotaged a NASA probe from discovering a pyramid on Mars. (TV: The Vault of Secrets)