Based upon the origins of urban planning from the Roman (pre-dark ages) era, the current discipline revisits the synergy of the disciplines of urban planning, architecture and landscape architecture, varying upon from the interlectural strategic positioning from university to university.
Another key role of urban planning is urban renewal, and re-generation of inner cities by adapting urban planning methods to existing cities suffering from long-term infrastructural decay.
Urban planning as an organized profession has existed for less than a century. However, most settlements and cities reflect various degrees of forethought and conscious design in their layout and functioning.
The development of technology, particularly the discovery of agriculture, before the beginning of recorded history facilitated larger populations than the very small communities of the Paleolithic, and may have compelled the development of stronger, more coercive governments at the same time. The pre-Classical and Classical ages saw a number of cities laid out according to fixed plans, though many tended to develop organically.
Designed cities were characteristic of the totalitarian Mesopotamian, Harrapan, and Egyptian civilizations of the third millennium BCE.
Distinct characteristics of urban planning from remains of the the cities of Harappa, Lothal and Mohenjo-daro in the Indus Valley Civilization (in modern-day northwestern India and Pakistan) lead archeologists to conclude that they are the earliest examples of deliberately planned and managed cities. The streets of these early cities were often paved and laid out at right angles in a grid pattern, with a hierarchy of streets from major boulevards to residential alleys. Archaeological evidence suggests that many Harrapan houses were laid out to protect from noise and enhance residential privacy; also, they often had their own water wells for probably both sanitary and ritual purposes. These ancient cities were unique in that they often had drainage systems, seemingly tied to a well-developed ideal of urban sanitation.
Ur, located near the Euphrates and Tigris rivers in modern day Iraq also had urban planning in later periods. The Greek Hippodamus (c. 407 BC) is widely considered the father of city planning in the West, for his design of Miletus; Alexander commissioned him to lay out his new city of Alexandria, the grandest example of idealized urban planning of the Mediterranean world, where regularity was aided in large part by its level site near a mouth of the Nile.
The ancient Romans used a consolidated scheme for city planning, developed for military defense and civil convenience. The basic plan is a central forum with city services, surrounded by a compact rectilinear grid of streets and wrapped in a wall for defense. To reduce travel times, two diagonal streets cross the square grid corner-to-corner, passing through the central square. A river usually flowed through the city, to provide water, transport, and sewage disposal. Many European towns, such as Turin, still preserve the essence of these schemes. The Romans had a very logical way of designing their cities. They laid out the streets at right angles, in the form of a square grid. All the roads were equal in width and length, except for two. These two roads formed the center of the grid and intersected in the middle. One went East/West, the other North/South. They were slightly wider than the others. All roads were made of carefully fitted stones and smaller hard packed stones. Bridges were also constructed where needed. Each square marked by four roads was called an insula, which was the Roman equivalent of modern city blocks. Each insula was 80 yards (73 m) square, with the land within each insula being divided up. As the city developed, each insula would eventually be filled with buildings of various shapes and sizes and would be crisscrossed with back roads and alleys. Most insulae were given to the first settlers of a budding new Roman city, but each person had to pay for the construction of their own house. The city was surrounded by a wall to protect the city from invaders and other enemies, and to mark the city limits. Areas outside of the city limits were left open as farmland. At the end of each main road, there would be a large gateway with watchtowers. A portcullis covered the opening when the city was under siege, and additional watchtowers were constructed around the rest of the city’s wall. A water aqueduct was built outside of the city's walls.
The collapse of Roman civilization saw the end of their urban planning, among many other arts. Urban development in the Middle Ages, characteristically focused on a fortress, a fortified abbey, or a (sometimes abandoned) Roman nucleus, occurred "like the annular rings of a tree" whether in an extended village or the center of a larger city. Since the new center was often on high, defensible ground, the city plan took on an organic character, following the irregularities of elevation contours like the shapes that result from agricultural terracing .The ideal of wide streets and orderly cities was not lost, however. A few medieval cities were admired for their wide thoroughfares and other orderly arrangements, but the juridical chaos of medieval cities (where the administration of streets was sometimes hereditary with various noble families), and the characteristic tenacity of medieval Europeans in legal matters, prevented frequent or large-scale urban planning until the Renaissance and the enormous strengthening of all central governments, from city-states to the kings of France, characteristic of that epoch. Florence was an early model of the new urban planning, which rearranged itself into a star-shaped layout adapted from the new star fort, designed to resist cannon fire. This model was widely imitated, reflecting the enormous cultural power of Florence in this age; he Renaissance was hypnotized by one city type which for a century and a half— from Filarete to Scamozzi— was impressed upon utopian schemes: this is the star-shaped city". Radial streets extend outward from a defined center of military, communal or spiritual power. Only in ideal cities did a centrally-planned structure stand at the heart, as in Raphael's Sposalizio of 1504 (illustration); as built, the unique example of a rationally-planned quattrocento new city center, that of Vigevano, 1493-95, resembles a closed space instead, surrounded by arcading. Filarete's ideal city, building on hints in Leone Battista Alberti's De re aedificatoria, was named "Sforzinda" in compliment to his patron; its twelve-pointed shape, circumscribable by a "perfect" Pythagorean figure, the circle, takes no heed of its undulating terrain in Filarete's manuscript. And, all this occurred in the cities, but ordinarily not in the industrial suburbs characteristic of this era (see Braudel, The Structures of Everyday Life), which remained disorderly and characterized by crowded conditions and organic growth. In the 1990s, the University of Kentucky voted the Italian town of Todi as ideal city and "most livable town in the world", the place where man and nature, history and tradition come together to create a site of excellence. In Italy, other examples of ideal cities planned according to scientific methods, are: Urbino, Pienza, Ferrara, San Giovanni Valdarno, San Lorenzo Nuovo.
Many cities in Central American civilizations also engineered urban planning in their cities including sewage systems and running water. In Mexico, Tenochtitlan, was the capital of the Aztec empire, built on an island in Lake Texcoco in what is now the Federal District in central Mexico. At its height, Tenochtitlan was one of the largest cities in the world, with close to 250,000 inhabitants.
Shibam in Yemen features over 500 tower houses, each one rising 5 to 11 storeys high, with each floor being an apartment occupied by a single family. The city has some of the tallest mudbrick houses in the world, with some of them being over 100 feet high (over 30 meters).
In developed countries (Western Europe, North America, Japan and Australasia), planning and architecture can be said to have gone through various stages of general consensus in the last 200 years. Firstly, there was the industrialised city of the 19th century, where control of building was largely held by businesses and the wealthy elite. Around 1900, there began to be a movement for providing citizens, especially factory workers, with healthier environments. The concept of garden cities arose and several model towns were built, such as Letchworth and Welwyn Garden City, the world's first garden cities, in Hertfordshire, UK. However, these were principally small scale in size, typically dealing with only a few thousand residents.
It wasn't until the 1920s that modernism began to surface. Based on the ideas of Le Corbusier and utilising new skyscraper building techniques, the modernist city stood for the elimination of disorder, congestion and the small scale, replacing them instead with preplanned and widely spaced freeways and tower blocks set within gardens. There were plans for large scale rebuilding of cities, such as the Plan Voisin (based on Le Corbusier's Ville Contemporaine), which proposed clearing and rebuilding most of central Paris. No large-scale plans were implemented until after World War II however. Throughout the late 1940s and 1950s, housing shortages caused by war destruction led many cities around the world to build substantial amounts of government-subsidized housing blocks. Planners at the time used the opportunity to implement the modernist ideal of towers surrounded by gardens. The most prominent example of an entire modernist city is Brasilia, constructed between 1956 and 1960 in Brazil.
By the late 1960s and early 1970s, many planners were coming to realize that the imposition of modernist clean lines and a lack of human scale also tended to sap vitality from the community. This was expressed in high crime and social problems within many of these planned neighbourhoods. Modernism can be said to have ended in the 1970s when the construction of the cheap, uniform tower blocks ended in many countries, such as Britain and France. Since then many have been demolished and in their way more conventional housing has been built. Rather than attempting to eliminate all disorder, planning now concentrates on individualism and diversity in society and the economy. This is the post-modernist era.
Minimally-planned cities still exist. Houston is an example of a large city (with a metropolitan population of 5.5 million) in a developed country, without a comprehensive zoning ordinance. Houston does, however, have many of the land use restrictions covered by traditional zoning regulations, such as restrictions on development density and parking requirements, even though specific land uses are not regulated. Moreover, private-sector developers in Houston have used subdivision covenants and deed restrictions effectively to create the same kinds of land use restrictions found in most municipal zoning laws. Houston voters have rejected proposals for a comprehensive zoning ordinance three times since 1948. Even without zoning in its traditional sense, metropolitan Houston displays similar land use patterns at the macro scale to regions comparable in age and population that do have zoning, such as Dallas. This suggests that factors outside the regulatory environment, such as the provision of urban infrastructure and methods of financing development, may play as big of a role in urban development as municipal zoning.
