Makkathran is the main city of Querencia, one of the planets in the Void that is populated by humans. Originally a sentient Raiel starship like the High Angel, after entering the Void it partially buried itself on Querencia and converted itself into a habitat for humans. At night the city is suffused with a 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.