Ideal city refers to a plan for a city that has been conceived in accordance with the dictates of some "rational" or "moral" objective.
The "ideal" nature of such a city may encompass the moral, spiritual and juridical qualities of citizenship as well as the ways in which these are realised through urban structures including buildings, street layout, etc. The ground plans of ideal cities are often based on grids (in imitation of Roman town planning) or other geometrical patterns. The ideal city is often an attempt to deploy Utopian ideals at the local level of urban configuration and living space and amenity rather than at the culture- or civilisation-wide level of the classical Utopias such as St Thomas More's.
Several attempts to develop ideal city plans are known from the Renaissance, and appear from the second half of the fifteenth century. The concept dates at least from the period of Plato, whose Republic is a philosophical exploration of the notion of the 'ideal city'. The nobility of the Renaissance, seeking to imitate the qualities of Classical civilisation, sometimes sought to construct such ideal cities either in reality or notionally through a reformation of manners and culture.
Examples of the ideal cities include Filarete's "Sforzinda", a description of which was included in his Trattato di Architettura (c. 1465). The city of Sforzinda was laid out within an eight-pointed star inscribed within a circular moat. Further examples may have been intended to have been read into the so-called "Urbino" and "Baltimore" panels (second half of the fifteenth century), which show Classically influenced architecture disposed in logically planned piazzas. Late nineteenth-century examples of the ideal city include the Garden city movement of Sir Ebenezer Howard, realised at Letchworth Garden City and Welwyn Garden City in England. Poundbury, Prince Charles' architectural vision established in Dorset, is among the most recent examples of ideal city planning.