For a long time, London was a small city. All its people lived inside the walls that were built by the Romans. This area is still called the City of London. There were many villages around the city. Gradually, more people came to live there. Then, step by step, the villages joined together into one huge city.
The city has a huge network of transport systems. The Victorians built a number of railway systems in the mid-19th century. Their main stations are in London, and the lines go to every corner of Great Britain. There were originally five major companies, which were merged into a national rail network in modern times.
There is also the world's first underground railway system, London Underground, which is the main way commuters get into London. There are five airports, though only one is actually in London (London City Airport). There is the London end of the London–Birmingham canal, which was important to the industrial 19th century.
Most people in London are British. However, London also has many immigrants. These people come from many different countries. They speak many different languages and have different religions and cultures. There are also many people from different countries who stay in London on business. Many people visit London as tourists. They may see the famous "Sights of London". These sights include palaces, churches and museums.
London is one of the world's most important cities for business, finance, and politics. It is also important for culture: media, entertainment, fashion, and art.