The mysterious prehistoric city
"Venice of the Pacific: The ruin consists of 92 artificial islets built on top of coral reefs, which are linked by a network of canals.
The meaning of the real name - "Nan Madol" means "the space in between," which references the canals.
The million dollar question: Why would someone build a city in the middle of the ocean.
One thing is for certain: It’s an engineering wonder, built entirely of giant basalt slabs in a time.
Impressive scale: The massive basalt walls are reportedly 25 ft (7.6 m) tall and 17 ft (5 m) thick in some places.
Megalithic architecture: Carbon dating indicates that some of the structures are around 900 years old.
Humans were there earlier: Evidence of the earliest human activity dates back to the first or second century BCE.
Where did all that basalt come from: The basalt stones are reported to have come from the opposite side of Pohnpei.
How was it transported: Modern archeologists have no idea how the massive stones.
It rivals the work of the pyramids: The effort required to build the megalithic structures would have rivaled that of the Egyptian pyramids.