Savannah is in the US state of Georgia, not the country, and it is the state's oldest city. General James Oglethorpe landed at Yamacraw Bluff on February 12, 1733, and laid out a town on a grid of small public squares that the city has mostly kept. Today 22 squares survive, inside one of the largest historic districts in the country. The wealth that built the houses around them came from cotton, rice and the labor of enslaved people, and the better museums here say so plainly.
It's a small, flat, walkable city, and three days is the right length: the squares, the house museums, Forsyth Park and a long lunch at a boarding-house table, plus one day out to Bonaventure Cemetery, Fort Pulaski and Tybee. A fourth day would mostly mean more squares. Many visitors come knowing the book and film Midnight in the Garden of Good and Evil. The house is worth a stop, but the city is bigger than the story.
Day one is the squares, Owens-Thomas House and the river. Day two is Jones Street, Mrs. Wilkes' lunch, the Mercer-Williams House and Forsyth Park. Day three is a day trip by car east to Tybee Island. We recommend starting on a Wednesday: the Owens-Thomas House is closed Mondays, Mrs. Wilkes serves lunch on weekdays only, and the Tybee lighthouse is closed Tuesdays, so Wednesday, Thursday and Friday work, with the coast on a Friday before the weekend beach traffic. Charleston is about two hours north and has its own plan: 3 Days in Charleston. Savannah also fits a longer trip through the United States.