In this episode of Pacific Pulse, Pacific correspondent for Australia Network news Sean Dorney explores one of the most mystifying places in the Pacific, the ruins of the dramatic lost city of Nan Madol on the island of Pohnpei in the Federated States of Micronesia. It's architectural magnificence is spread over a network of more than 90 tiny islands, criss-crossed by canals. The question is, who built this ancient city, which dates back to at least the twelfth century.