"Her body was found at the bottom of the property which opens out into a woods," a police source said, adding that foul play was suspected.
The house in the town of Palaiseau, 17 kilometres (10 miles) south of Paris, was rented on popular home-sharing website Airbnb by a group of friends who made the grisly find on Saturday.
The woman was found "hunched in a dug-out area, her head against the ground, covered in branches and surrounded by wood stumps", said the source.
She was dressed, but was not wearing shoes and had a "ring with a large stone" on her finger. No documents which could allow her to be identified were found.
The body's advanced state of decomposition meant it was not possible to determine cause of death, and an autopsy will be carried out, said the source.
The Airbnb renters were being questioned by police on Sunday.