Architecture is both the process and the product of planning, designing, and constructing buildings or other structures. Architectural works, in the material form of buildings, are often perceived as cultural symbols and as works of art. Historical civilizations are often identified with their surviving architectural achievements.
The practice, which began in the prehistoric era, has been used as a way of expressing culture for civilizations on all seven continents. For this reason, architecture is considered to be a form of art. Texts on architecture have been written since ancient time. The earliest surviving text on architectural theory is the 1st century AD treatise De architectura by the Roman architect Vitruvius, according to whom a good building embodies firmitas, utilitas, and venustas. Centuries later, Leon Battista Alberti developed his ideas further, seeing beauty as an objective quality of buildings to be found in their proportions. Giorgio Vasari wrote Lives of the Most Excellent Painters, Sculptors, and Architects and put forward the idea of style in the Western arts in the 16th century. In the 19th century, Louis Sullivan declared that "form follows function".