One of the oldest archaeological sites not on a heritage list, this Pacific state, like Easter Island, is an engineering marvel We zigzag slowly in our skiff around the shallow coral heads surrounding Pohnpei. The island, a little smaller than New York City, is part of the Federated States of Micronesia. It is nestled in a vast tapestry of coral reefs. Beyond the breakers, the Pacific stretches 5,578 miles to California. A stingray dashes in front of us, flying underwater like a butterfly alongside our bow. Our destination is Nan Madol, near the southern side of the island, the only...