Local legend says that you will die if you spend the night there. But once this was home to the nobles and priests of the Saudeleur dynasty, which ruled Pohnpei's 30,000 inhabitants up until about 500 years ago, according to William S. Ayres, an archaeologist at the University of Oregon.

Dr. Ayres said that Nan Madol was constructed out on the reef, starting about 1,500 years ago, partly because people had been living out there for hundreds of years to have easy access to the sea, and, perhaps more important, to better commune with ocean deities.

The columns for the walls were quarried on Pohnpei, he said, and floated out to the reef on rafts, about 500,000 tons in all over the 1,000 years of construction, Dr. Ayres has estimated. While most of the islands were living quarters for priests, others were given over to special purposes like making canoes, preparing coconut oil or, most grandly, burying royalty in tombs with courtyards surrounded by 25-foot walls.