tower, structure, the greatest dimension of which is its height. Towers have belonged to two general types. The first embodies practical uses such as defense (characteristic of the Middle Ages), to carry bells, beacons, or antennas, and to utilize maximum floor space in a given area, as in modern skyscrapers. The second type is used to symbolize the authority and power of religious and civic bodies, as in the churches and town halls of Europe; skyscrapers also perform a similar function for modern corporations. The earliest use of tall structures for ritual and symbolism is seen in the Babylonian ziggurat. The temple architecture of India had a variety of pyramidal and cylindrical masonry towers. The many-storied pagoda in wood was a part of early Chinese and Japanese temple architecture. The minaret belongs to Islamic religious architecture. Used for defensive purposes in the early Middle Ages in Western Europe, towers with massive masonry walls served as refuges and lookouts. Many 9th- and 10th-century round defense towers remain in Ireland and a few in Scotland, including one at Brechin. Castles had their donjons or keeps, of which the 11th-century Tower of London shows a high development. Of the fortified towers that Italian nobles built even for their city dwellings numerous examples remain, notably at San Gimignano. The earliest existing church towers in Europe were those of the 5th and 6th cent. in Ravenna, Italy. There the bell tower, or campanile, stood detached from the church building itself; another example is the celebrated bell tower at Pisa (1174). In English and French Romanesque churches a high tower rises over the crossing of nave and transepts, and the west end generally possesses lower twin towers. The relatively simple Romanesque towers generally had square or round shafts with many blind arcades in horizontal tiers and were topped by a simple octagonal or conical spire. They developed into the higher, elaborate type of Gothic, decorated with pinnacles and canopied niches. Towers of extreme lightness and intricacy were developed in the late Gothic period, as in the cathedrals at Rouen, Vienna, and Antwerp. With the Renaissance the classical orders were incorporated into tower design. Particular success was attained in the tapering pyramidal compositions of Sir Christopher Wren's numerous London towers, including those of St. Paul's Cathedral. English churches, e.g., St. Martin-in-the-Fields by James Gibbs, set the pattern for the typical New England church with the wooden tower and steeple rising directly over the entrance vestibule. In the 20th cent. towers have often taken the form of skyscrapers. Notable modern towers of varied design and function include the highly original Einstein Tower at Potsdam by Erich Mendelsohn and Frank Lloyd Wright's Johnson tower with glass tubing at Racine, Wis.