A room aboard the Enterprise that surrounds its users with realistic simulated outdoor environments, an early forerunner of the holodeck seen in the animated series.
The recreation room appears in the episode The Practical Joker. It is a large empty chamber that can project a chosen setting, complete with weather and terrain, around the people inside it.
After the Enterprise passes through an energy cloud while escaping Romulan ships, the main computer begins playing tricks on the crew. McCoy, Sulu and Uhura go to the recreation room for a walk in the woods and find themselves locked in.
The computer turns their scene into a blizzard and then a hedge maze, and they are in real danger from the cold before a rescue party cuts through. The idea of an environment room that traps its occupants returned many times once The Next Generation introduced the holodeck.