The Temple of Olympian Zeus took over 650 years to finish — started in the 6th century BC, completed by Hadrian in 131 AD. Of the original 104 columns, 15 still stand; a 16th fell in a storm in 1852 and lies exactly where it landed. Hadrian's arch nearby reads: "This is Athens, the ancient city of Theseus" on one face, "This is the city of Hadrian" on the other. A Roman emperor desperate enough for legacy that he carved it in marble.
Julian Lupyan, CC0, via Wikimedia Commons