By Julia Wheeler
BBC News, Dubai
The Pearl Carpet was created in the late 1860s
A carpet that was commissioned in India 150 years ago to decorate the tomb of the Prophet Muhammad in Medina is due to be auctioned in Qatar.
The rug, known as the Pearl Carpet of Baroda, was created using an estimated two million natural seed pearls.
It is decorated with hundreds of precious stones, including diamonds, sapphires, rubies and emeralds.
Bidding is expected to start at about $5m but experts say its eventual selling price could be far higher.
Tradition has it that the Pearl Carpet of Baroda was commissioned by India's wealthy Maharaja of Baroda as a gift to sit at the tomb of the Prophet Muhammad.
The maharaja's death meant it was never delivered and remained in India, being exhibited as a highlight of the Delhi Exhibition more than 100 years ago.
Later, it was taken by a family member to Monaco.
The tiny natural pearls, known as Basra, were harvested from the waters of the Gulf.
Created in the late 1860s, it is largely red and blue with swirling vines of flowers and three large round rosettes across its centre.
The carpet is to be auctioned in Doha on Thursday by Sotheby's.
The auctioneers say it is not inconceivable that the carpet could fetch as much as $20m.
Whoever the new owner is, it is unlikely the carpet will sit on a floor - it is expected to be used as a wall hanging.