STONE

   The Neolithic era of Prehistoric architecture has traditionally been called the "Stone Age" because of the appearance of stone tools and other implements, as well as large-scale stone constructions. The earliest masonry structures are Neolithic settlements from around 3100 BC, such as the one at Skara Brae, located on the Orkney Islands off the coast of Scotland. This island had little forestation, and its rocky coastline provided ample masonry for this seaside village. Houses were built in square shapes with rounded corners, made with layers of flat stone stacked without the use of mortar and slanted slightly inward to create a partial corbel. The smaller roof opening was then thatched. Inside the rooms, stone was used to create partitions for bedding and niches for storage. A hearth area with a low stone bench was located in the middle of the room. The houses were linked with covered passageways. Tomb mounds were also created from large rocks, called megaliths, and were placed into a post-and-lintel structural system to create passageways into the tomb interiors. Such monumental rocks were often transported large distances, and furthermore, the fact that different types of stones came to symbolize different aspects of society demonstrates the beginnings of a socially stratified culture with codified rituals. Stonehenge, located in the Salisbury Plain of Wiltshire, England, dates to around 2750 BC and is the most famous example of a large-scale stone monument.

   The Inca of Peru devised a unique and structurally superior method of stone construction as seen at the mountainous town of Machu Picchu, Peru, built around AD 1450. Here the stone buildings are all of a superior dry stone construction technique called ashlar, in which massive stones are cut to fit perfectly together without mortar. Irregularly shaped rocks fit at perfect junctions while the walls lean slightly inward, which is characteristic of Inca construction. Despite the severe earthquakes and the pillaging of Inca stonework to build Spanish churches in Peru, surviving Inca wall junctions remain perfectly tight with no spaces or cracks or threat of collapse. Making these architectural feats more impressive is the fact that the Inca did not have the wheel or the horse, and therefore used manpower and llamas to drag large rocks up these mountains.

   Despite the prevalence of stone monuments across almost all cultures, stone structures came to be primarily associated with Ancient Greek and Ancient Roman architecture because of the beautiful white marble found mainly in the area around Greece. The term megalith comes, in fact, from the Ancient Greek encounter with these large (mega) stones (lithos). Subsequent stone constructions built throughout the Middle Ages and in the Renaissance then came to recall this enduring classical history and to express an alliance with the papacy or the Holy Roman Empire. The use of stone to signify architectural authority continued in the early-20th-century Beaux-Arts style, when architects such as Richard Morris Hunt and Charles Follen McKim, inspired by the idealized but temporary "White City" constructed for the World's Columbia Exposition held in Chicago in 1893, went on to build stone structures across the major East Coast cities of the United States, including the Metropolitan Museum of Art in New York City and the Public Library in Boston. Although more recent buildings are formed from steel skeletons and feature curtain walls of glass and other materials, stone is still often used to provide a more historically based, "grand" curtain wall for buildings.

   See also BRICK.