All aboard! During the 1800s, when construction of the Philadelphia Zoo was reaching a feverish pitch, another fantastic invention was nearing completion: the transcontinental railroad. Today, our youngest visitors can share in the excitement of this grand accomplishment with a quaint ride on the [brand new] SEPTA PZ Express - a charming but SEPTA-fied reminder of the Zoo's heritage. Valid SEPTA Key cardholders ride FREE when they present their valid SEPTA Key card at the SEPTA PZ Express entrance. Cannot be combined with another offer.