Tiaanamat

Tiaanamat was a large inhabited asteroid, orbiting the planet Akhaten in its rings.

Tiaanamat played host to the Festival of Offerings, a millennial choral ceremony held when the planet's rings aligned.

The Eleventh Doctor and Clara Oswald visited the vast, winding markets of Tiaanamat, as he had done previously in his first incarnation with his granddaughter. (TV: The Rings of Akhaten)

Behind the scenes
The asteroid is not named in the series itself. The name "Tiaanamat" comes from production artwork on the BBC website. According to handwritten notes on the artwork, the asteroids in the Rings of Akhaten are composed of solidified molten magma ore fragments. Tiaanamat was built on the largest piece of ore on the outer ring as a docking point.