| During the twentieth century, there were great improvements in engineering technology. |
| These new developments allowed the construction of many amazing tunnels, bridges, towers, and office buildings. |
| For centuries, people had dreamed about the possibility of connecting the island of Great Britain to the mainland of Europe. |
| However, it was only in 1994 that such a link was completed, |
| when a tunnel was dug under the English Channel, between England and France. |
| The Channel Tunnel, also known as the “Chunnel”, |
| actually consists of three separate railway tunnels. |
| These tunnels are about 50 kilometers long. |
| They are located about 150 meters below the bottom of the sea. |
| Obviously, this was an extremely challenging project to undertake. |
| As a result of the Chunnel, it is now possible to travel between London and Paris by train. |
| And the trip takes only three hours, |
| of which only 20 minutes are spent inside the tunnel! |
| A suspension bridge is a bridge that is supported by strong wires that hang from tall towers. |
| The world’s longest suspension bridge is the Akashi-Kaikyo bridge, near the city of Kobe, Japan. |
| This bridge is nearly 4 kilometers long, and the two towers near the middle of the bridge are about two kilometers apart! |
| It took almost 20 years to design this bridge, and 10 years to build it. |
| This bridge was designed to withstand extremely strong winds, |
| because Japan often experiences wind storms called typhoons. |
| The bridge was also designed to withstand powerful earthquakes, which sometimes hit Japan. |
| At the beginning of the twenty-first century, |
| the world’s tallest free-standing tower was the Canadian National Tower, or the CN Tower. |
| The CN tower is 553 meters tall. |
| It is located in the city of Toronto, within the Canadian province of Ontario. |
| This structure was built in 1975 as a television and radio tower. |
| Before the CN tower was built, TV and radio reception in the Toronto area was poor. |
| This was because the TV and radio signals were blocked by the buildings of downtown Toronto. |
| When the CN tower was built, this problem was solved. |
| Of course, the CN tower is also a famous tourist attraction. |
| People can ride in the very fast elevators that take them to observation areas, |
| which are at about 350 and 450 meters above the ground. |
| Although the CN Tower is the world’s tallest tower, it is not an office building. |
| The tallest buildings in the world are the Petronas Towers, in the city of Kuala Lumpur, Malaysia, |
| and the Sears Tower, in the American city of Chicago. |
| The Sears Tower, which is 442 meters tall, was completed in 1974. |
| It has 110 floors, and its top floor is the highest office floor in the world. |
| However, the Petronas Towers reach slightly higher, to a height of 452 meters. |
| The Petronas Towers were completed in 1998. |
| Obviously, the late twentieth century witnessed some amazing achievements of engineering. |
| It will be very interesting to see what new wonders will be constructed in the twenty-first century! |
