America's oldest summer theatre - Lebanon's only professional theatre. Gretna Theatre has been your home for summer theatre and entertaining audiences across South Central Pennsylvania since 1927! Gretna Theatre is located in the arts/resort community of Mt. Gretna, PA. Featuring a mix of Broadway musicals, comedies and dramas as well as musical revues and theatre for children, Gretna Theatre currently operates at the Mt. Gretna Playhouse during the months of June, July and August each summer, and presents special events and educational outreach programming at other venues during the balance of the year.