Like others here, I arranged a trip with Pohnpei Surf Club for a vehicle from Kolonia to take us to Nan Madol. After getting near the site, we paid about 3 USD to the family who lives there, before walking about 15 minutes on a stone path (very slippery when it's pouring rain, like it was the day we went). As we get closer, huge walls made of columnar basalt seem to emerge out of the jungle. Finally, we approach the main islet - Nan Madol is made of several artificial islets criss-crossed by a series of canals, but most visitors only go to one islet, Nan Douwas - and what an islet it is! Enormous, imposing walls surround a central tomb, built for the first member of the dynasty that created Nan Madol, and a further set of outer walls as well, with remnants of structures in between the two walls. If this were in most other countries, it'd be a standout hit with tens or hundreds of thousands of visitors, but because Micronesia is so hard to get to, it gets very few - we were the only visitors we saw at the site that day. The temptation to make a comparison to Easter Island is obvious - while nothing on Pohnpei quite matches the artistry of the moai, no structure I saw on Easter Island matches the ones built at Nan Madol.