Just south of downtown Atlanta, there's a small cemetery in the middle of a cloverleaf ramp to I-75. The 'headstones' represent slave graves from a plantation that was on the site, but no one's sure about the number of people that could be buried there--one report says possibly a thousand. The Atlanta paper has a story about it from 2012:
https://www.ajc.com/news/local/gone-and-almost-forgotten-slave-graves-along/KVbIDEC86ZLcff8iJrOVLN/