In England, Scotland, and Ireland during the Iron Age (after 500 B.C.), lake dwellers constructed fortified settlements on mounds built up in shallow lakes or marshes. These forts are called crannogs, from the Old Irish word crann, “tree.” Near Glastonbury in England, a mound was created by laying thousands of trees on the lake bed. The mound was anchored by piles, covered with a wooden platform on which thatched huts were built, and surrounded by a palisade fence.

Some primitive peoples of today build their houses on platforms supported by piles. Such dwellings are built over lakes, rivers, and lagoons in the East Indies, central Africa, and tropical South America.