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, such as the Great Pyramid of Giza, (TV: The Daleks' Master Plan et al) were well known to other races.

One splinter of Scaroth claimed to have caused the pyramids to be built, (TV: City of Death) though the Doctor was skeptical of this claim. (PROSE: A History of Humankind) The Osirans 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)

The Rings of Akhaten also had a pyramid, a holy site for the Sun-singers of Akhet, seven planets orbiting the same star, all of them sharing the belief that life in the universe originated on that pyramid. In it was a mummy. (TV: The Rings of Akhaten)

The Monks came to Earth in a pyramid from where they could manipulate their simulated worlds. (TV: The Pyramid at the End of the World)