For the Slack Bay premiere at the Cannes Film Festival last weekend, Blake Lively was spotted donning an icy blue tiered dress with a floral-embellished bodice from designer Vivienne Westwood, looking every part like a modern Cinderella. A tousled updo with a sparkly hairband and Christian Louboutin heels completed her look. Check out these 10 gowns that will have you look equally princess-like.