Vertiform City was a holographic city created by the USS Enterprise-D's computer in 2370.

The city was a metaphorical representation of an area abundant in vertion particles, namely Tambor Beta-6, a white dwarf star. It was so named because of the presence of vertion particles in the star. However, when the star proved to be an insufficient source of the particles, the train on the holodeck changed its destination to New Vertiform City. (TNG: "Emergence")

Vertiform City was never actually shown on screen.