A holodeck, in the fictional Star Trek universe, is a simulated reality facility located on starships and starbases. The first use of a "holodeck" by that name in the Star Trek universe was in the pilot episode of Star Trek: The Next Generation, "Encounter at Farpoint", although a conceptually similar "recreation room" appeared in an episode of Star Trek: the Animated Series.
In the timeline of the fictional universe, the concept of a holodeck was first shown to humans in an encounter with the Xyrillan race in the Star Trek: Enterprise episode "Unexpected".
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