Carraya IV was the inhabited fourth planet in the Carraya system. This system was located in the Carraya sector. This remote planet's location, close to Romulan space, was shown on a map from Deep Space 9 that was displayed on the bridge of the USS Enterprise-D. Carraya IV hosted a dense jungle and was home to the arboreal needle snake.
Klingon survivors from the Khitomer Massacre were brought to a secret Romulan prison camp here following the battle, and eventually learned to live in peace with their Romulan captors. The planet contains several lush jungle areas, and was not heavily fortified apart from a few Romulan soldiers. Supply ships made regular stops at the world.
The colony was kept secret until 2369, when a Yridian information dealer named Jaglom Shrek approached Lt. Worf with knowledge of the camp during an USS Enterprise-D visit to Deep Space 9. Shrek believed Worf's father, Mogh, was alive on Carraya IV, leading Worf to investigate. He found the colony and was initially held captive there, but was allowed to return to the Federation with several Klingon youths who wished to leave their secluded home. They were brought to the Enterprise aboard a Romulan Warbird, and sworn to secrecy about the prison camp in order to protect the honor of the Klingons who remained behind. (TNG: "Birthright, Part I", "Birthright, Part II", "Rightful Heir")
Background information Edit
"car-EYE-ah" was the pronunciation for this planet's name from the script pronunciation guide for "Birthright, Part I". 
According to the Star Trek Encyclopedia (3rd ed., p. 67), "The exterior of the prison camp was designed by Richard James, from which a model was built that was the basis for a matte painting exectured by Dan Curry. (Production designed James, of course, also responsible for the full-size interior sets, as well.)" The first edition of the Star Trek Encyclopedia (p. 43) stated that James Magdaleno was, as well, involved with the design of the prison camp.
According to the Star Trek: Star Charts (p. 62) and the Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), the Carraya system was located in the Beta Quadrant.