Caves are important in many areas of science. Earth scientists study how rock forms and changes in caves. Biologists visit caves, too, to learn about the unusual species that live in them.

However, caves are important for another reason. On the walls of some caves are paintings. They were made by people who lived thousands of years ago. Some of the earliest paintings, like the ones in EL Castillo Cave in Spain, are forty thousand years old. Some are outlines of hands or simple designs. Others show animals or people hunting. They were painted using natural red, orange, white and black minerals. These works of art connect us with people who lived long ago.

Interestingly, most of these cave paints were not found by scientists. They were found by people exploring caves for fun. For example, the cave paintings in Lascaux, France, were found in 1940 by a group of boys. They had no idea that the pictures they found on the walls of the cave were over seventeen thousand years old. Over the years, people have found these types of amazing paintings in sites all over the world.

You can explore these caves, too. Some have become very popular tourist sites. They are easy to visit and have underground tours for the public. However, exploring other caves can be more difficult. You must be careful, and you need to be prepared for cold, darkness and danger. And you might have to walk through mud or water. Dress warmly and bring special equipment, such as helmet with a light. But these underground worlds are so fascinating that it is worth the trouble.

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Almost everyone has read about the Taj Mahal in India. It is one of the most beautiful buildings in the world. Over three hundred years ago, Shah Jehan built the Taj Mahal as the tomb for his wife. Shah Jehan wanted his wife's tomb to be perfect. He did not care about time or money. He brought together workmen from all Asia. Altogether, over 20,000 men worked on the building, and it took them over seventeen years to finish it.

The building rests on a platform of red sandstone. Four thin white towers rise from the corners of the platform. A large dome rests from the centre of the building. Around this large dome there are four smaller ones.

The building is made of fine white and coloured marble. It has eight sides and many arches. There is an open corridor just inside the outer walls. From this corridor, the visitor looks through the marble screen to a central room. The bodies of Shah Jehan and his wife lie in a tomb below this room.

A beautiful garden surrounds the Taj Mahal. The green trees make the marble look even whiter. In front of the main entrance to the building there is a long, narrow pool. If you look in this pool, you can see all the beauty of the Taj Mahal in the reflection from the water.

Many people think the Taj Mahal is the most beautiful at sunset. Then the marble picks up the colour of the sunset, and the building and its reflection in the pool gleam like red jewels.