Urban areas have become more crowded as societies leave rural living in the past. Children from rural and suburban areas leave home to find their fortune in cities when small communities are no longer economically feasible. Businesses tend to be in larger cities because they have a concentrated customer base. While the digital age has somewhat changed that factor, it is still a valid way to choose a location.
Space is very limited within urban areas, and it is also very expensive. Developers and land owners want to get as much money as possible for each square foot. That is why buildings have become taller with each passing year. The amount of ground space is limited, but height is only limited by the skills of man to create stable buildings reaching into the sky.
Builders in urban areas understand the needs of their clients for safe, affordable buildings. The foundations are several levels deep to ensure the weight of the building will be properly supported. Concrete is a favored building material in this case. Cement, a dried aggregate of small rocks and silica sand are combined with water to make this sturdy building material. Silica sand is often used because it is commercially available in many areas and has a history of mixing well in concrete. Steel rebar is added to walls and floors for additional strength. As the buildings are raised, each level contains a concrete floor to support exterior walls. Interior supports are a combination of steel trusses and concrete columns. This makes the affordable to build as well as durable to maintain.
Skyscrapers continue to be built in large cities. These buildings often house thousands of people during the work day. Even apartment buildings are now being built on this massive scale. Rather than travel throughout the city for food, clothes or other necessities, these buildings offer services in small shops. Many apartment buildings now contain restaurants, grocery stores, cleaners and entertainment services within the walls. Large office buildings now offer a variety of restaurants and other service businesses for office workers during the day. Modern skyscrapers are truly becoming cities in a building.