MadreDeDios (Spanish: Mother of God) is a desert world with artificially generated atmosphere. Father Federico de Soya was assigned to the small town of Nuevo Atlan on the Llano Estacado on MadreDeDios prior to being recalled to service in the Pax Fleet.
In this provincial stone-and desert world, the entire population was mostly Catholic, but not Pax born-again Catholic. Instead, the people were part of a break-away movement called the Mariaists. One century before the lifetime of Father Capitan Federico de Soya, their ancestors had left the planet of Nuevo Madrid when that world had voted to join in the Pax and have its Christian churches submit to the Vatican. 
Its main economic activity was ranching. MadreDeDios suffered an outbreak of the Red Death, and offworld retrovirus that swept the colony on the planet. Father Federico de Soya's sister, when a child, was infected. The Mariaist medics were said to be able to do nothing except pray.
Later, during the time of the protagonists of Endymion, the Llano Estacado is said to have been abandoned, and the ranches all empty. Ciudad Del Madre's population is down to a few dozen, consisting exclusively of Pax researchers to see if the world is worth terraforming.
- Llano Estacado, an isolated region on the planet.
- Cuidad Del Madre, a town in the windswept southern reaches of the Llano Estacado