Queen SofiaThis diamond tiara set in gold and silver in a floral motif is actually convertible: it can be a necklace and the center flower can be a brooch. Sofia (switching now to the regular Spanish spelling of her name, rather than the Greek Sophia) wore it as a necklace for her pre-wedding ball, and I'm not sure she's ever worn it as such again.
Sofia using the tiara as a necklaceYou know, I think she really doesn't have time to play around with the convertible properties of this piece; it's kept in fairly constant use as a tiara. The Spanish collection of tiaras is not exactly small but it isn't overflowing with tiara riches either, so the ladies do a lot of sharing. This seems to be the most shared piece in the family. If there's a tiara event at which all of the Spanish royal ladies are present, it's nearly a guarantee that this one will be making an appearance.
Infanta Elena borrowed it mostly in her younger years; these days, she usually wears the tiara she received as a wedding gift from her (now ex-) husband's family.
Infanta CristinaThis seems to be Infanta Cristina's favorite tiara, as she wore it on her wedding day and has continued to do so since. Of course, Cristina doesn't own a tiara of her own. Princess Letizia wears it now too; it's currently her second most-worn tiara. (She does have her own now, but we haven't seen her wear it.)
Princess LetiziaDiamond floral tiaras are pretty common, but I think this one is a definite contender for the best floral tiara prize. It's delicate, but it's a great size and has good dimension. It looks good on a whole range of face shapes and hairstyles. Plus, it's convertible (which is awesome, even if you don't ever convert it).
Where does this rank on your list of favorite floral tiaras?