On a remote Pacific island not much bigger than Manhattan, there are ancient pyramids built out of living coral. New evidence reveals that these tombs could be up to 700 years old — much older than experts had previously thought. The royal tombs are tucked away in an artificially built ancient city called Leluh just off the mainland of Kosrae, a Micronesian island. Leluh was home to Kosraean high chiefs (as well as some lower chiefs and commoners, too) from about 1250 until the mid-1800s, when foreign whalers, traders and missionaries started to arrive on the island. With impressive canals...