A terraformed Federation colony modeled on the Scottish highlands, home of Beverly Crusher's grandmother Felisa Howard.
Caldos IV is one of the Federation's first terraforming projects, a colony designed to recreate the look and traditions of Scotland, with stone houses and a weather control system to keep its climate stable. Beverly Crusher's grandmother, Felisa Howard, lived there as a healer.
In Sub Rosa, the Enterprise brings Crusher to Caldos IV for her grandmother's funeral. Crusher falls under the spell of Ronin, an anaphasic life form that had been attached to the women of her family for generations, and the colony's weather control system begins to fail as Ronin's influence grows. Crusher eventually destroys him.