Nan Madol is the most extraordinary archaeological site in the Pacific. Built between roughly 1200 and 1500 CE on a reef flat off the southeast coast of Pohnpei, it consists of more than a hundred artificial islets constructed from massive basalt columns, linked by canals wide enough to paddle a canoe through. At its height it housed the ceremonial and political centre of the Saudeleur dynasty, a ruling class that governed Pohnpei for three centuries before being overthrown.
The name means "spaces between" — a reference to the channels threading through the complex. The largest islet, Nan Douwas, was the royal mortuary complex and retains walls up to eight metres high. The basalt columns, each weighing several tonnes, were stacked like logs without mortar and have resisted more than half a millennium of wind, rain and vegetation. The whole site feels inexplicable: an urban centre built on open water, in a place with no flat land, using materials transported from across the island. UNESCO inscribed it as a World Heritage Site in 2016. A local guide is not optional — the site is labyrinthine and much of its meaning is carried in oral tradition.