20 to 43 feet (6 to 13 meters). They
have shiny, green leaves and large, white
flowers.
Citrons look like large lemons. They
have whitish pulp. The rind has a thin
outside layer and a thick inside layer.
Citron trees grow to about to about 11.5
feet (3.5 meters) tall. They have pale
green leaves and purple or white flowers.
Uses
Citrus fruits are a healthy food because
they are rich in vitamin C. Many people
eat citrus fruits raw or squeeze them to
make juice. People also use citrus fruits
to flavor drinks and cooked dishes. In
addition, citrus fruits may be canned or
made into jam.
Citrus rinds provide oil that may be
used as a flavoring or in making perfume
and medicines. Rinds may also be
cooked with sugar to make candy.
#More to explore
Fruit • Grapefruit • Lemon • Lime
• Orange
City
A city is a place where many people live
closely together. City life has many benefits.
Cities bring together a great variety
of people from different backgrounds.
They offer more jobs, more schools, and
more kinds of activities than smaller
towns and villages. But cities also can be
dangerous and polluted.
About half the world’s people live in
cities. Tokyo, Japan, has more people
than any other metropolitan area. (A
city’s metropolitan area includes the city
itself and other places close by.) New
York City is the largest city in the
United States.
City Features
A city’s central business district, or
downtown, usually has its tallest office
buildings and biggest stores. The downtown
area is often the oldest part of the
city. A city usually has one or more areas
of factories and warehouses (storage
buildings) outside of downtown. Most
of the city’s homes lie still farther from
downtown.
More than
100 million
tons of citrus
fruits are produced
every
year. Oranges
make up more
than half of
the total.
BRITANNICA STUDENT ENCYCLOPEDIA City 123
Cities usually have a variety of places for
entertainment and relaxation. These
include museums, concert halls, theaters,
parks, and sports arenas.
Cities commonly have a public
transportation system to help people get
around without cars. Public
transportation includes buses, trains,
and subways. Subways are trains that
run underground.
Built-up areas called suburbs lie outside
the boundaries of most cities. Suburbs
tend to have more houses and apartments
than businesses. Many people live
in the suburbs and commute, or travel,
to their jobs in the city.
City Government
Like countries and states, cities have a
government. A city government usually
includes a group of elected lawmakers
called the city council. Most cities also
elect a leader called a mayor. In other
cities the city council names a leader
called a city manager.
City governments provide many services.
These include police protection,
firefighting, hospitals, and schools.
Tokyo and its surrounding areas have more people than any other city in the world.
Suburbs usually have more
houses than businesses. People
who live in the suburbs often
work in a nearby city.
124 City BRITANNICA STUDENT ENCYCLOPEDIA
Many cities also support museums and
libraries.
City Problems
Cities attract people looking for work,
education, and other ways to improve
their lives. But city life can also be hard.
Not everyone shares equally in the benefits
of the city. Some people live in rundown,
overcrowded housing. Others
have no homes at all. They sometimes
live on city streets. Crowded living conditions
in cities also lead to crime, traffic,
and pollution.
History
About 5,500 years ago people in Mesopotamia
(now Iraq) started the first cities.
Rome (now in Italy) may have been
the largest ancient city. Between
250,000 and 1.6 million people lived
there.
Some cities in ancient times and in the
Middle Ages (AD 500–1500) were independent
of any country. They were
called city-states. City-states ruled themselves
and the surrounding area. Athens
and Sparta were major city-states of
ancient Greece. From the 1000s to the
1400s Florence, Venice, and other citystates
were important in what is now
Italy. After the Middle Ages these cities
lost their independence. Today almost
all cities belong to a particular country.
The Industrial Revolution, which
started in the late 1700s, contributed to
the growth of cities. New machines
invented during this period made manufacturing
an important business. Many
people from the countryside moved into
cities. They looked for work in newly
built factories.
In the late 1800s architects invented
new building methods that changed the
way cities looked. Tall buildings called
skyscrapers appeared in many cities.
During the 1900s cities continued to
change. They grew rapidly in
population. They also spread outward.
Many people moved to the suburbs.
Some highly populated areas became
known as megalopolises. Megalopolises
often include several cities and many
suburbs.
#More to explore
Architecture • City-State • Government
• Industrial Revolution • Pollution
• Skyscraper • Transportation
Ruins of an ancient city called Harappa
stand in present-day Pakistan. Harappa
was one city of the Indus Valley civilization,
which lasted from about 2500 BC to about
1700 BC.
