Philadelphia’s Weccacoe Playground will soon be transformed into a historic memorial in honor of thousands of freed slaves. Discovered back in 2008 by historian Terry Buckalew, the community playground originally served as an African American Burial Ground for members of the Mother Bethel African Methodist Episcopal Church — which was purchased by the church in 1810. Archaeologists believe that an estimated 5,000 freed black slaves are buried 18 inches beneath the concrete, according to Associated Press.