Gartner's duct is a remnant from the embryonic development of the urinary system (specifically, the mesonephric or Wolffian duct).
Typically, Gartner's duct runs along the anterolateral walls of the vagina. Cysts can form from persistent portions of this duct.
While often associated with the vaginal walls, Gartner's duct remnants and their cysts can extend or present in adjacent structures. Based on the provided options, the cyst is stated to be usually located in the Labia minora.
Therefore, the usual location for a Gartner's duct cyst, considering the options and the provided correct answer, is the Labia minora.