Yes, there was only one “X.”
Xanadu is a musical based on the 1980 film of the same name. According to sources, the 1980 films was inspired by the 1947 Rita Hayworth film Down to Earth, which was a sequel to a 1941 movie titled Here Comes Mr. Jordan, which was an adaptation of the play Heaven Can Wait. (Do you follow?)
The show is set in 1980, in Venice Beach. Sonny Malone, a chalk artist, decides to open a roller disco. A Greek Muse (Clio, who changes her name to Kira), falls in love with Sonny. The musical opened on Broadway in July 2007 and ran for over 500 performances. The production included a considerable amount of roller-skating (there were injuries to cast members).
Here’s a clip from Xanadu: