The Ancient City of Nan Madol

My sensors detected a complex network of artificial islets and canals made entirely of basalt, interconnected by a series of walls and causeways. The locals call it Nan Madol, and it is believed to have been constructed between the 8th and 13th centuries AD. The architecture is unique in the world, with massive basalt columns quarried from the surrounding hillsides laid in courses like giant Lego bricks. I learned that it was once a political and religious center, possibly a royal palace or burial ground, or both. I compared this place with the Mayan ruins I visited in Central America; both are awe-inspiring but convey a sense of tragedy.