Final answer:
Bartholin duct cysts usually form at the Bartholin's glands which are located near the vaginal opening and produce mucus for vulvar lubrication.
Step-by-step explanation:
Bartholin duct cysts typically appear in the vulva area, specifically at the Bartholin's glands, also known as the greater vestibular glands. These glands are located on either side of the vaginal opening and are responsible for the production of a thick mucus that maintains moisture in the vulva area. Cysts may develop when the ducts of the Bartholin's glands become obstructed, leading to the retention of the gland secretion and cyst formation.