The salient feature of New York is its towers, and it was con sidered wise, in framing the zoning law, to permit the erection of a tower, which may rise to an indefinite height (limited only by structural possibilities and economic conditions), upon 25% of the total lot area. This has resulted in a very surprising and interesting form of architecture (q.v.). In Paris certain buildings of a monumental nature, either religious or governmental, may exceed the height limit. In London, towers purely for architectural embellishment but not for human occupancy, may pass the legal height. In New York no restriction is made as to occupancy of the tower provided that the building remains within the given "envelope." Furthermore, the so-called "dormer" permit allows certain portions of the front of each building to rise slightly in excess of the maximum vertical height to give variety of outline. Above this the buildings are usually stepped back, forming a pyr amidal series of terraces which vie with the storeyed magnificence of the hanging gardens of Babylon. The law has produced two other interesting results : first, the virtual elimination of interior light courts, these being cut in the side in order to preserve a base for the central tower ; second, the tendency to assemble larger and larger plottage so that the 25% tower will be large enough to war rant construction of a great number of tower storeys.
The example of New York has been followed in hundreds of American cities, where no part of city planning has been so popu lar as zoning. No effect of zoning has impressed itself on the public consciousness more than its effect on the architectural treatment of buildings.
The important needs in connection with the further develop ment of zoning, as a means of promoting art and amenity in con nection with city building, whether directly owing to extended power under restrictive legislation, or indirectly by further use of existing powers, are : the inclusion of zoning as part of com prehensive city plans so that it will deal constructively with build ing expansion and reconstruction of complete urban areas corn prising all parts of a city or a region ; the further extension of zoning in regard to restriction of density, parallel with further strengthening of provisions in regard to heights and uses, so as to secure more light and air in buildings, a better display of buildings and less congestion on adjacent streets than at present. Further restriction on height should be based on the principle that the primary need is to obtain adequate spaces about buildings of all heights, and not to obtain lower buildings as an object in itself. (See also TOWN AND CITY PLANNING.)