One of the most imposing pieces in a collection full of imposing pieces, this pearl and diamond tiara was referred to as the Diadem of Ancient Pearls in Russia's imperial family. Made in the early 19th century, it is a complicated structure of Brazilian diamonds and ancient pearls, with a graduated top line and a center row of dangling pearl drops. As originally worn the tiara is shaped tightly and forms a near-complete circle.
The pearl diadem was last worn by the last tsarina, Alexandra Feodorovna. Some have referred to it as her favorite tiara, which I've always found an intriguing statement as she was known for her rejection of the grand court life, a point of contention between the empress and the ladies of the court. Whatever her feelings on this piece, its grand scale was certainly fitting for her place. That same scale would probably make it a very rarely worn tiara if it existed in an active royal family today - but we'll never know, as it was collected with the rest of the imperial jewels by the Bolsheviks when the revolution hit and it's been lost ever since.
Where does this rank on your list of favorite pearl tiaras?