tiny islets of Nan Madol were built on top of a coral reef, at Leluh, coral was actually incorporated into the construction material of many buildings, including the royal tombs. [8 of the World's Most Endangered Places]

"Today, the ancient tombs of the royal burial complexes are one of the few parts of the ancient Leluh site that remain intact," said Zoe Richards, a coral expert at the Western Australian Museum and lead author of a new study detailing the findings. "Much of the historical site is overgrown by the tropical forest and has succumbed to hundreds of years of tropical weather and tidal inundation, and some parts of the site have been dismantled and reused in modern construction."

These tombs, also known as saru, stand about 6.5 feet (2meters) tall, and they're shaped like frustums (pyramids with their pointy tops lobbed off). Historical sources indicate that when a Kosraean king died, he would be rubbed with coconut oil and wrapped in mats and cords to be buried in the saru for up to three months. The king's bones would then be exhumed, cleaned and reburied in a hole on the nearby reef, Richards and her colleagues wrote.

Because these burials were not permanent, not much was left behind in the tombs to help archaeologists today determine the age of these structures. The bones of a 50-year-old man and a dog were found in one of the tombs, known as Inol-1, but a radiocarbon dating of those skeletal remains showed that this burial took place relatively recently, sometime