Pierre Casiraghi and his girlfriend, Beatrice Borromeo, made it official on Saturday when they got married in a civil ceremony at Monaco's Pink Palace. The couple, who have shared plenty of sweet moments in their six years together, later celebrated their nuptials with a garden party at the palace. The event, which <a href="http://www.people.com/people/package/article/0,,20395222_20937921,00.html?xid=popsugar" >Prince Albert called "mostly informal," was held outdoors and had a carnival theme. Their "low-key" wedding will be followed by a**ther, more lavish Ceremony and reception on Beatrice's family's private island in Italy next weekend.