The commission came on the heals of and bore a strong resemblance to unbuilt structures that he had designed for Lincoln Park in Chicago. Both projects included an aviary, aquarium and cages for various animals. The Pittsburgh Zoo, like most zoos of the period were designed primarily as a showcase for exotic animals and did not have the same function of modern zoos. Cages were sparse and little attention was given to recreating the animal's natural habitat.
Silsbee's zoo structure was a commanding structure situated in a prominent hilltop location in the park. A series of terraces and broad stairways create a formal approach to the main building. Silsbee was responsible for the design of the stairs and likely oversaw the design of the lighting and landscape features as well. The main building was a sprawling symmetrical brick Romanesque structure with a hipped roof and flanked by two octagonal pavilions attached to the main building with curved colonnades.
The building was finely detailed and one of the few examples of Silsbee's large-scale civic projects that was actually constructed as well as evidence of Silsbee's role as in urban design and campus planning. Detailed photos of the structure at the University of Pittsburgh indicate that the clearstory windows were composed of several panes of glass arranged in a cruciform shape. Crisp arches create openings in the building facade at two end bays. A copper cornice and gutter with copper-formed anthemion accents surrounds the main structure. The interior, lit with a skylights, was sparse except for display cases and other cages for animals. The side pavilions had open cages on all sides and were topped with a clay tile roof. The same kind of detail that was found on the main building can be found in the landscape. Monumental stone steps and low curving walls form terraces. These are accented with podiums and a serious of lighting fixtures. Given Silsbee's flair for the exotic, it would be interesting to know the origin of the griffin light poles that once flanked the main staircase.
With changing attitudes about the role of zoos in our society, came new structures more amenable to the needs of animals. Sadly, many of the early monumental zoo structures were demolished to make way for subsequent buildings. Due to their specific design and layout, they were not easy to adaptively reuse as offices or other functional structures so few of these large buildings survive as an educational tool and testament to the careful consideration and resources given to this important cultural institution.