High-resolution photogrammetry image of the Newark Octagon and Observatory Circle-Newark, Ohio. The circle is approx 1050' in diameter, and each wall of the Octagon approx 585' long. Just a portion of the massive Newark Earthworks.
Built by the Hopewell 2000-2400 yrs. ago.
Historians estimate that the pyramids of Giza are roughly 5000 years old. This can't be verified for certain because you can't carbon date limestone.
You can, however, carbon date an eggshell. This one, found in Aswan, is 7000 years old, and depicts the pyramids beside the Nile.