It's not every day that an It Girl European princess turns 21, so of course her highness threw a bash to be rivaled. The chic soiree hosted by Princess Maria-Olympia of Greece and Denmark brought the stylish likes of Paris and Nicky Hilton, Lauren Santo Domingo, and Poppy Delevingne to an estate in the English countryside dripping with giant balloons and flowers. The dress code? "Revolutionize Your Black Tie," and indeed, the guests did not disappoint. Extravagant headpieces, rainbow platform sneakers, and even a body-paint tuxedo all made an appearance at the garden party turned full-on rager. 

The #5021Revolution bash also celebrated the birthday of Olympia's father, Prince Pavlos, who turned 50 on May 20th, and if there's anything the fashion crowd loves more than a princess, it's a Crown Prince. No wonder Mr. Valentino Garavani himself came through.

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[Photo via @olympiagreece]