Lelu Island, connected to the larger island of Kosrae by a causeway, is where a massive walled city was built between the 13th and 14th centuries for Kosraean royalty. Lelu's ruins, including burial mounds and dwellings, are hidden behind thick tropical vegetation, in the kind of isolated setting you might imagine trekking hours through dense jungle to find.
You can still see the dwelling compounds of the high chiefs, two royal burial mounds, a few sacred compounds and numerous large walls, built from huge hexagonal basalt logs stacked like a log cabin. On-site signs tell the full story.