6. Underwater Cairn
A large stone structure was discovered in 2003 underneath the Sea of Galilee composed of giant monoliths that weigh over 60,000 tons. No one knows what the structure might have been used for, although most cairns in the area were used as burial sites. According to researchers at the Ben-Gurion University, the cairn dates back over 4,000 years and could have been used as a fortified settlement before it was lost to the sea.