Carbon dating indicates that the construction of Nan Madol began around 1200 CE, while excavations show that the area may have been occupied as early as 200 BCE. Some probable quarry sites around the island have been identified, but the exact origin of the stones of Nan Madol is yet undetermined. None of the proposed quarry sites exist in Madolenihmw, meaning that the stones must have been transported to their current location. It has been suggested that they might have been floated via raft from the quarry, and a short dive between the island and the quarries shows a trail of dropped stoneS...There's a paper on dating the stones on the Academia website, but I didn't sign in to download it, due to my own laziness. Not much of a mystery here.
LOL, 250 million tons of magnetized basalt logs weighing up to 50 tons each used as the sole architectural material in a complex bigger than Giza on an island without fresh water containing manufactured tunnels to other islands - and none of the engineering requirements of its creation has been explained, especially supposedly by natives living in grass huts and transporting themselves in canoes.
No mystery here?
Whatever.
It has been suggested that they might have been floated via raft from the quarry, and a short dive between the island and the quarries shows a trail of dropped stoneS...
Dang it, you tease the "magic dragon" idea and than shoot it down with the raft and dropped stones, dang it :)