The Calder System lies on the Beta Quadrant side of the Federation, very near to the Romulan Neutral Zone. It is considered a largely untamed area due to the existence of a nearby nebula, Samuel's Nebula, which disrupts use of sensors and communications, making navigation very difficult and creating a sort of safe haven for pirates, fugitives, rogue enemies, black market dealers, and other such scum of the galaxy.
The Calder system it self is composed of a Class G star and 7 orbiting planets- Nariko, Olivia, Lowell, Una, Quentin, Urania, and Fenton. The system also sports a ring of ice asteroids on it's distant edge known as Morrigan's Ice Belt.
What really puts the Calder System on the map are two things. Firstly, it's archeological significance, having Proto-Romulan ruins on the second planet in the system, and secondly, the presence of a recently constructed station, Starbase 60, which has established a strong presence in the system.