The Three Minute Cities were settlements on Gallifrey, connected to the Capitol via rail. The Time Lords who hailed from them were highly regarded, (PROSE: The Infinity Doctors) and at least one of the Cities was used for meeting alien delegations. (PROSE: The Gallifrey Chronicles)
Marnal Gate wrote about the Three Minute Cities in his novel Valley of the Lost.
In at least one universe, Olyesti was one of the Three Minute Cities. (PROSE: The Infinity Doctors)