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A rejuvenation center is a recreational area on a Colonial ship meant for recreation by a general crew.
On the Galactica, this area was used by both pilots and the ship's general crew, as opposed to the exclusive Officer's Club frequented solely by officers and Colonial Warriors. The rejuvenation center contained gaming tables with various games (such as compartment bulyarks), as well as various refreshments, and was housed away from the ship's hull.
When a Cylon kamikaze attack caused internal fires to break out around the ship, the rejuvenation center was cut off from the rest of the ship. This left Lieutenant Boomer, Athena, Boxey, the robotic Muffit II and roughly a dozen personnel unable to escape the fire. Had it not been for the efforts of Apollo and Starbuck, as well as the effort of Muffit II to bring the trapped personnel breathers, the blaze would have killed everyone in the rejuvenation center (TOS: "Fire in Space").