The fort is open for tours and, as part of the National Park system, the entry fee is very reasonable.
From Fort Moultrie, Fort Sumter can be seen. Fort Sumter is accessible only by ferry and is a bit more expensive to access, although worth the visit as well.
Location: 32°45'36.84"N 79°50'25.15"W
Distance from downtown Greenville: 220 miles