http://en.wikipedia.org/wiki/Nan_Madol# ... nd_tourism
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. However, no one has successfully demonstrated or explained the process. Some modern Pohnpeians believe the stones were flown to the island by use of black magic.
Emphasis mine. Basically, there's this "city" built in the water there and nobody knows how or why. I find it fascinating. Every time I look at that area of the map now, I'll be thinking of weird stones. And who knows, maybe the black magic is why your recent invasion of the place failed.
Do a Google image search, the aerial photos are pretty neat.
