Nan Madol is an ancient city located on the eastern shore of the island of Pohnpei, in the Federated States of Micronesia. The city was constructed around 1200 AD and is comprised of a series of man-made islets separated by narrow channels and enclosed by sea walls. The ruins of the city, which was once the center of the Saudeleur dynasty, are considered one of the most impressive archaeological sites in the Pacific.

The city is believed to have been a center of political and religious power for the region for several centuries. The buildings and structures at Nan Madol are made from huge basalt stones, some of which weigh up to 50 tons. The construction of the city involved transporting these massive stones from distant quarries and assembling them into complex architectural structures.

The city contains several impressive buildings, including tombs, ceremonial platforms, and stone-faced walls that surround the islets. It also has a network of canals that connected the islets to the open sea. These canals allowed for the movement of people and goods between the different parts of the city.

Today, the ruins of Nan Madol are a popular tourist attraction, and visitors can explore the site with the help of local guides. The area surrounding the city is also a popular destination for snorkeling and diving due to its clear waters and diverse marine life. The site was designated as a UNESCO World Heritage Site in 2016.