Nan Madol is an ancient stone city that was built on tidal flats off Temwen Island on the south-east coast of Pohnpei, in the Federated States of Micronesia. It comprises 92 man-made islands which were built over a period of 300 years from about the 12th to 15th centuries and were occupied up until about 1800. The islands were built by hauling massive hexagonal shaped basalt columns from other parts of Pohnpei and using the columns to create retaining walls, between which coral rubble was dumped to form foundations for stone buildings. Nan Madol can only be reached by boat, although you can wade through the water from Temwen Island at low tide. Even when you arrive by boat from the ocean side, as we did here, expect to do some wading in the water to reach the islets.