The northern waters around the British Isles are dotted with ancient artificial islands that range in size from 30 to 100 feet (9 to 30 meters) in diameter. Known as "crannogs," these islands were created with tons of rock and debris, and typically featured round structures built over the water. Archaeologists originally thought that most crannogs dated to the Iron Age, as far back as 800 B.C. Recently, however, radiocarbon dating of ancient ceramics found underwater near crannogs has pinpointed their origins at about 3640-3360 B.C. This means that at least some cranogs were built during the Neolithic period -- long before the construction of Stonehenge's famous stone circle, pegged at around 2500 B,C.
Mystery of ancient islands:
- Crannogs can be found in rivers, lakes, and estuaries throughout Ireland and Scotland. The Scottish Crannog Centre says they were created by the monumental task of pounding piles of rock into the muck.
- Archaeologists have catalogued the remains of hundreds of these waterside islands, most of which are now covered by trees. Some appear as faint mounds that peek up from just below the water's surface.
- Some of the ancient ceramic vessels were found intact, and showed signs of charring -- leading some archaeologists to believe that the sites were used for religious rites, funerals, or celebratory feasts.