This summer, Two Rodeo Drive—the tony Beverly Hills shopping destination that looks like a faux European thoroughfare—set up an exhibit with Galerie Michael of 12 Salvador Dali sculptures that attracted hundreds of thousands of people.

During the three-month exhibit of surrealist sculptures, the shopping mecca promoted the social-media hashtag #Dali2Rodeo, generating a total reach of 4.2 million on Twitter and Instagram as art aficionados and shoppers snapped pictures of the artwork and posted them.