December 25 is Christmas Day(圣诞节). Christmas is an important holiday in many countries. On Christmas Day, most families get together for a big dinner. They give presents to each other and visit friends. The Christmas tree is an important part of the Christmas holiday. Most families buy trees. The families decorate(装饰) the tree together. Parents usually tell their children that Father Christmas comes during the night and brings presents to good children. Of course, Father Christmas isn't real. The parents of the children are really "Father Christmas". They put the presents under the tree or into their children's stocking(长统袜) after the children go to sleep.

    Do you have a nickname (昵称) ? Most of us do by our looks, clothing, or personality. But for cities, the meaning of their nicknames has much more than that.

    Many big cities have nicknames, such as New York--The Big Apple, London--The Great Smog, and Rome--The Eternal( 永恒的) City. Why do cities have such nicknames?

    In the 1920s, there were many races in New York. People called the prizes of these races apples. Writer John J. Fitz Gerald first called New York the Big Apple, because New York is the place that many people dreamed of going to for the biggest prize of all.

    For Rome, as the name suggests, the answer is simple. Romans believed that no matter what happened to the world, Rome would go on forever. Rome has been an important center of power for more than 2,000 years.

    As for London, in the Victorian period, it had problems with its air. Later in 1952, serious air pollution made 10,000 people fall ill. But now the air of London has become better.

    Does that sound interesting? Does your city have a nickname?

    Stonehenge means "hanging stones". They stood in a circle, with 30 more stones lying on top to form a ring of rocks. There was also an inner circle built with similar stones. The stones set up in a trilithon(巨石牌坊) pattern.

    A trilithon is made of two stone pillars with a stab of rock laid across the top. The stones weigh up to 20 tons each. People wonder how the huge rocks were placed that way.

    Historians agree that Stonehenge was built in three different stages. The first stage took place about 5, 000 years ago. At that time, a large circular earth wall was made. Historians believe the wall was dug and cut with tools made form anglers(鹿角) of red deer. The earth wall was about 98m in diameter(直径) a 5-meter-tall stone was placed near the center. Then, they had to transport the large blue stones (up to 4 tons) 384 kilometers to Stonehenge. Experts think they might be moved across ice and snow. The ground in winter in this area is usually full of ice and snow, making it easier to move the rocks. The next task was to stand the stones up. The most difficult task was putting the top stones in place. Each one of these tasks took a lot of planning and a lot of strength, but the workers of Stonehenge were excellent builders.

    Why was the monument built? Some scientists think it's a burial ground. There are over 400 graves (burial sits) nearby. A man was buried with two gold earrings which are the oldest gold ever found in Britain (dated to 2470 BC). Others think Stonehenge was built by early astronomers. Scientists believe that when a person stands in the center of the monument, the changing of seasons can be seen. Certain stones mark the location of the rising and setting moon in midwinter. Other stones mark the rising and setting sun in midsummer. The ancient people held religious ceremonies on these days. These ceremonies probably asked the gods to bring good weather for crops and to protect the people from bad weather.

    Stonehenge is an engineering success. Thousands of years later, it still stands. As a calendar, Stonehenge is very accurate. It shows that early people had a deep understanding of the movements to the sun and the moon. They didn't have machines or computers, but Stonehenge shows people could do many things using only their muscles and their brains.