The final installment of the Butler Area Public Library’s “Summer in the City” series will be a groovy one.

Retrofest will feature music from the 1950s to 1980s, a costume contest among those who dress in the garb of their favorite decade, a trivia contest and photo ops.

The event will be held from 6 to 8 p.m. Aug. 23, in the library courtyard, 218 N. McKean St., Butler.

The event is free and open to the public.