The Kaybin District was a city district on Denobula known for its nightclubs, sometimes called "Kaybin bars", where, during the Denobulan mating season, one could find intimate companion(s). These establishments were open all night.
In 2151, Doctor Phlox recommended the Kaybin bars along the river in a letter to his Interspecies Medical Exchange colleague Dr. Jeremy Lucas, who had recently moved into living quarters in that area of Denobula. However, Phlox advised Lucas not to enter the Kaybin bars unescorted, as what happened inside them could be very disturbing to uninitiated visitors. (ENT: "Dear Doctor")
In 2153, Phlox mentioned Lucas' experiences in the Kaybin District in another letter, when talking about his occasional loneliness on Enterprise and his desire to be with other Denobulans again. (ENT: "Doctor's Orders")