Prospect Park's correspondence between geological structure and landscape characters or type is contrasted with the correspondence between geometric structure and landscape characters at the U.S.Capitol Grounds. Here, the structure of the encompassing city plan designed by L'Enfant-a grid with radiating diagonal-and the plan organization of the existing governmental edifice provide an armature for three landscape characters-the Beautiful, the Picturesque, and the Sublime. The space straddling the central axis and located between the capitol and the mall was a beautiful, smooth greensward flanked by allees of sycamore lining the extensions of Maryland and Pennsylvania avenues. The northern and southern grounds were densely planted Picturesque plantations of shrubs and trees, trough which service drives and walks curved sinuously uphill towards the east forecourt. Within the plantations, two rusticated stone ventilation towers and a hexagonal brick grotto functioned as architectural follies and hygienic services for members of Congress and their constituents.