Modern building has become so universally conditioned by optimized technology that the possibility of creating significant urban form has become extremely limited.

Many of the received models of modern architecture and planning owe their ultimate origin to the building code and public health reform movements of the second half of the 19th century.

From the Berlin tenement reform law of 1897 to H. P. Berlage's plan for Amsterdam South of 1917, designers and theorists in Germany and Holland moved toward the development of a perimeter residential block that would preserve the plastic continuity of the street while opening up the resultant courtyard for use as an enclosed semi-public space.