The preferable position for these buildings is at the side of the open space rather than in the centre. In this latter position the necessity of a framing for the remaining portions of the space holds good. Porticoes and porches, which can be carried out into the street openings, help to close in the frame. Errors in scale, especially unduly large open areas, are to be avoided. Convexity of the open space is inadmissible.
Concavity is preferable.
Each open space should, as far as practicable, be laid out individually. Combinations of spaces are subject to various requirements, according to the purpose for which each is intended, e.g. whether it be for purposes of traffic or as a site for monumental buildings. The grouping of several separate spaces can be made to produce fine effects from an artistic point of view. The formal and informal cities of the Romans. The irregular cities of the earlier Middle Ages.