sentences:  Free daytime concerts occur frequently in the summer, and an ice skating rink is set up for winter months.In 1987, during The Joshua Tree Tour, U2 held a free concert in Justin Herman Plaza to "Save the Yuppies" following the Black Monday financial crisis in October.During the finale of the impromptu concert, Bono spray-painted graffiti on "Vaillancourt Fountain", for which he was fined.