Dwarfed only by a temple mound in Illinois, the sacred hill known as the Emerald Mound was once a well-appointed holy site, but is now just a flat octagonal expanse. 

Originally constructed between the 1200s and the 1700s, the elevated place of worship was built by the Plaquemine Native American culture. The mound is believed to have been topped by eight ceremonial stone structures with two larger ones at either end of the long rise, and three smaller ones lining the sides. The central mount itself rises 65 feet above the surrounding ground and excavation of the area has revealed animal bones and ceramics that have led researchers to believe that the area was used in ritual activity. 

None of the original structures remain on the otherwise nondescript summit as the site seems to have been abandoned during the 1700s either due to religious or tribal division or possibly due to a die-off from European viruses. Whichever the case, the Emerald Mound still stands, once a place of holy ceremony, now a geographic memorial.