The best museum in Atlanta, bar none, Atlanta History Center spans centuries' worth of Southern history, from the Civil War era right up to the 1996 Atlanta Olympics. Spread across 33 forested acres in Buckhead, the complex includes the famed Cyclorama (see photo above, and explanation below), 22 acres of walking trails and gardens, as well as two historic homes. Most notable is the Swan House (see below), a stately old mansion built in 1928 for the Inman family. The interactive Smith Family Farm uses character reenactments to show firsthand the troubles that families faced during the Civil War. Through photos, videos, talks, folk art, and other memorabilia, visitors get a raw look at the extensive history of Georgia and the South as a whole. That visit is complimented by the galleries in the main building museum, which explore other aspects of the war.
In February of 2019, the center opened its new, circular space, purpose-built to house a painting 42-ft. tall, 358 ft. in circumference, and 10,000 lbs. This panorama, known as the Cyclorama, was at one time the largest oil painting in the world, and it portrays the Battle of Atlanta, a bloody engagement fought on July 22, 1864, during which the Confederates and Yankees lost more than 12,000 men combined. A fascintating, 12-minute film is projected onto the painting every hour, on the hour, telling how the piece was created by German painters, on behalf of boosters of the Union, and how it was reworked over the years (at one point to make it look like the Confederates won the battle).
The Margaret Mitchell House, the former home of the "Gone with the Wind" author, is also part of the museum, though it's on a separate campus five miles away. The estate is massive so you'll need from several hours up to a half day to fully take advantage. There's free parking in the museum lot.