Makkathran is the main city of Querencia, one of the planets in the Void that is populated by humans. Originally constructed by an alien race, nonetheless it is suitable for habitation by humans, although some dimensions are not, for example stairs and doorways.Also, at night the city is diffused with an ubiquitous orange light.

As Edeard's powers grow, and he becomes more familiar with the city, he discovers that the city appears to have some form of awareness of its inhabitants and can respond to Edeard's requests to reshape stairs, or even walk through walls or sink through floors.

A map (Archived) of the city is available from Hamilton's official site.

Spoilers: what the city really is
At the very end of The Evolutionary Void, it is revealed that the city is a sentient starship, like the High Angel.
Community content is available under CC-BY-SA unless otherwise noted.