Until the time of our great-great-grandparents, each region's architectural style was largely defined by its particular culture, climate and natural resources. Materials and construction techniques developed only very slowly, if at all. With all their buildings being built the same way, cities and towns naturally developed a strong sense of aesthetic unity.

The places that have been able to retain this quality -- such as Prague, Paris, Charleston and the Greek hill towns -- have something that in today's world makes them prime tourist destinations. However, the mechanized production of building materials, advances in construction methods and the increasingly swift evolution of architectural styles has meant that since great-great-grandfather's day, buildings erected by successive generations often look very different indeed.

Nonetheless, the 20th century saw a conscious attempt at generating aesthetic unity. The International Style is a term coined in the 1930s to describe a key branch of the Modernist movement. The style had its origins in avant-garde, socialist movements in post-World War I Europe and was characterized by crisp, boxy forms, a lack of color and ornament, large windows and flat roofs. There was a strong emphasis on function as a key determinant of the building's design, and the thinking was that this way of making buildings could be applied universally to any culture or climate.

The International Style produced many of the last century's great buildings, but in the hands of less-talented architects, the application of functionalist design principles often led to the creation of soulless, uncomfortable buildings. This caused particular problems in Britain and the United States, where these principles were often applied to large, low-income public housing projects.

The end of Modernism as a movement is often traced to the dynamiting in 1972 of Pruitt-Igoe, a public-housing complex in St. Louis, Mo., designed by Minoru Yamazaki. Despite being designed in accordance with classic Modernist principles, after years of problems the complex was declared uninhabitable and demolished.

The event signaled a loss of faith in functionalism, and indeed an end to attempts to define universal design values. The advent of what became known as postmodernism resulted in a proliferation of movements, approaches and personal styles. Design aesthetics now had to be judged on their own merits rather than against any pre-existing standards. Taken further, some contemporary architects even reject the idea of a personal style of their own, attempting to begin each project with no preconceptions of how it will look.

Tokyo is now being reshaped by a series of massive, multi-building developments, such as the Shiodome project in Shinbashi and Mori Buildings' Roppongi Hills, both in Minato Ward. These projects exemplify what might be described as the 21st-century equivalent of the International Style. However, rather than applying a universal principle as that movement did, what we see now is high-profile architects traveling the world deploying their own -- rather than a universal -- design style juxtaposed with each other.

In the mix-'n'-match cultural blender that is contemporary Japan, this can result in odd combinations of architects. The design of one of the blocks in the Shiodome project, for instance, pairs Jean Nouvel, the Paris-based architect of sleek, ultramodern buildings, and the American Jon Jerde, best-known for his populist, crowd-pleasing designs for malls and shopping centers.

What we must, apparently, conclude from this is that even though these huge developments could have harmonized the same ideas and aesthetics for their various buildings, overall aesthetic coherence is no longer a priority. It seems that while we may want aesthetic unity (even the artificial, Disneyfied unity of Odaiba's Venus Fort) where we holiday or relax, we are drawn to diversity where we live and work.