Alien ruins may be found in orbit around a planet or blackhole, within an asteroid, buried in the desert, encased in ice within an ice cave, or in other unusual terrain. These ruins may feature advanced technology or may more closely resemble ancient ruins of our own history and be made of stone or some other fantastic material. Alien ruins may have ancient automated systems that still function. They may have teleportation portals that lead to other locations across space and time. They may contain alien artifacts. They may have been abandoned because of a threat (creature, celestial event, warring faction) that may or may not still be present.

When designing alien ruins, consider first what the original purpose of the structure was. It may be an ancient defense installation, a mine, a powerplant, a research station, or something else. Often in narratives explorers of alien ruins do not at first realize the purpose of the site. Next consider the reason the structure is now in ruins.