That's Bob the rock. He has a brother but they took him away.
If it is Wright Square, in the historic center, it is the grave of Indian Chief Tomochichi, who they moved to put in a monument. He gave the land to the settlers for Savannah.
It is likely from one of many quarries that used to operate in the region. When I was in high school it was one of the meet up spots for local teens.
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