Philadelphia Zoo featured on Ghost Hunters tonight

Given it's long, rich, and often-emotional history, it's no surprise that many consider Philadelphia to be among the most haunted cities in the United States.

Often, paranormal sightings and activities are linked to the town's Revolutionary War era landmarks, such as Fort Mifflin, City Tavern, and St. Peter's Church Cemetery. Or the Gothic, fortress-like confines of Eastern State Penitentiary (opened in 1829).

One landmark that has gone virtually unexplored up until now is the Philadelphia Zoo.

"America's First Zoo" was chartered in 1859. It's opening was delayed by the Civil War, with the gates finally opening on July 1, 1874.

Tonight, the first ever paranormal investigation of the zoological grounds will be featured on Ghost Hunters (9 p.m. on SyFy). The episode was filmed in early April.

Locations explored include the Solitude House, which was built by John Penn (grandson of city founder William Penn) in 1784. Predating the opening of the zoo by nearly 100 years, the structure is said to have quite a history. In more recent years, it housed reptile exhibits.

(For more on the Solitude House and its ongoing restoration, see this recent article from the Philadelphia Inquirer.)

Also featured will be the Penrose Building, which formerly functioned as a research laboratory and vet hospital, and the Shelly Building, now used as administration offices.

Reportedly, the zoo staff has experienced a wide range of potentially-paranormal activity over the years, including flickering lights and several reports of partial and full-bodied apparitions roaming the aforementioned buildings  and the zoo's winding outdoor pathways.

No animal spirits are thought to be haunting the grounds, but it should be interesting to see what otherworldly evidence - if any - Jason Hawes, Grant Wilson, and crew are able to uncover...