Kasterborous

Kasterborous (Cas-TER-bor-os) was the constellation in which the planet Gallifrey was located. (TV: Pyramids of Mars) When explaining where he was from, the Doctor sometimes mentioned that Gallifrey was located in Kasterborous. (TV: Attack of the Cybermen, Voyage of the Damned)

The constellation was named by the Minyans. As no Time Lord was allowed to know Gallifrey's personal future, TARDISes were prevented from entering Kasterborous after a certain date. (PROSE: Goth Opera)

Penelope Gate and Ulysses owned a summer house in the Kasterborous of another universe. (PROSE: The Infinity Doctors)

Behind the scenes
Кастерборус
 * It has been suggested that the design on the back of the TARDIS key (as worn by the Third, Fourth and Eighth Doctors) is a representation of the constellation, with Gallifrey's twin suns the central star in the pattern.
 * The word "constellation" is used in reference to Kasterborous as a fixed location. However, the word "constellation" normally means an alignment of stars as seen from a subjective location. By this logic, the Kasterborous constellation could only be seen from one planet. It seems that Robert Holmes intended it to mean "Kasterborous Sector" or "Kasterborous System", but the term "the constellation of Kasterborous" has been used as recently as Voyage of the Damned.