Monument Falls is a spectacular 80-foot waterfall found in the headwaters of Long Swamp Creek, west of Monument Falls Road. It lies on private property, off limits to the general public. One way to gain access to the falls is by staying at the "Bearfoot Falls" rental cabin just north of the falls. It may also be possible to gain permission to access the falls from Sharptop Cove Young Life Camp, located downstream, but I've never tried this approach. 

To learn about more waterfalls in the Jasper area, see chapter 3 in Mark Ozboyd's "Waterfalls of Georgia" guidebook.