The shape and type of a CBD almost always closely reflect the city's history. Cities with strong preservation laws and maximum building height restrictions to retain the character of the historic and cultural core will have a CBD quite a distance from the city center. This practice is quite common for European cities such as Paris, Moscow, or Vienna. In cities in the New World that grew quickly after the invention of modern transportation such as road or rail, a single central area or downtown will often contain most of the region's tallest buildings and act both as the CBD and the commercial and cultural city center. Increasing urbanization in the 21st century have developed megacities, particularly in Asia, that will often have multiple CBDs scattered across the urban area. It has been said that downtowns (as understood in North America) are therefore conceptually distinct from both CBDs and city centers. Although no two CBDs look alike in terms of their spatial shape, however, certain geometric patterns in these areas are recurring throughout many cities due to the nature ofa78 centralized commercial and industrial activities.