Decked out in one of his grandfather's bespoke suits and a white silk scarf, Lapo Elkann worked his charm on the crowd at the Gramercy Park Hotel's Private Roof Club on Wednesday night. "I was born here, and this city has always been extremely important in my private and professional life," said the Fiat heir turned entrepreneur. Diane von Furstenberg, whose children are cousins of Elkann's through their shared Agnelli heritage, and Anna Wintour, who featured the young dandy in a ten-page spread in this month's Vogue, co-hosted the airy affair to toast the U.S. launch of Elkann's design company Italia Independent. In the crowd were industry heavyweights such as Carolina Herrera, Calvin Klein, and Christian Louboutin, as well as social darlings like Fabiola Beracasa and Zani Gugelmann, who swung by for a look at the eligible bachelor before hitting the Whitney's Art Party at Skylight Studios.

"Of course, I have an inner hippy," said Rosario Dawson at the musuem's Summer of Love-themed shindig. "And she wishes she could sing like Janis Joplin." Others in the crowd—which included Sarah Michelle Gellar, Kate Bosworth, Emmy Rossum, and Julia Restoin-Roitfeld—settled for dressing like the 1960's icon in floor-sweeping floral gowns, caftans, and headbands. For Chiara Clemente, though, there wasn't quite enough psychedelic chic in the house. "I expected much more color," said the filmmaker, who wore a tangerine Katy Rodriguez dress. "But I guess New Yorkers just can't give up black."

The previous evening, Theory's Meatpacking District store was packed with a fashionably green set for the label's Icon Project environmental awareness benefit. Robert Kennedy, Jr., offered guests like Karen Elson, and Olivia Chantecaille earth-friendly tips during his impassioned keynote address. "When I had my minivan, I got 22 miles per gallon and spent $2,200 on gasoline a year," said the senior attorney for the National Resources Defense Council, the evening's co-sponsor. "Now my Prius does 48 miles to the gallon, and gas costs me $1,000." His words resounded with fellow Prius driver Rain Phoenix. "My car is the greenest part of my life," said the actress and lead singer of the papercranes. "I also try to limit my environmental damage by touring with my band in a bio-diesel bus and picking up vintage clothes whenever I can."

— Sarah Cristobal (Elkann) and Jessica Ramakrishnan (Whitney and Theory)