1 . Named “America’s Finest City” due to its hospitality, beauty and ideal climate, San Diego is located on the border with Mexico. The residents are so active outdoors that it is called “Sportstown, the U.S.A.”. San Diego’s 70 miles of beaches are a heaven for swimmers, surfers, divers, boaters and sunbathers. Another favourite outside activity is golf. With 100 courses (about 50 of them public), San Diego is a golfers’ paradise. Many San Diego residents came here first as tourists, who were attracted by San Diego’s sunny beaches, nearby mountains and deserts, plus the cultural delights of any big city. The world-famous San Diego Zoo, SeaWorld Adventure Park, Wild Animal Park, museums and other attractions attract visitors from around the world.

The zoo is home to some 4,000 animals, including the world’s largest group of parrots. Animals are displayed in natural settings, and there is a petting zoo for children. By contrast, the Wild Animal Park is a wildlife preserve with an area of over 2,000 acres and more than 3,000 free-roaming (自由漫步的) animals in natural habitats.

In addition to housing the zoo, Balboa Park is home to several museums and attractions, including an aerospace museum, an art and history museum, the Old Globe Theatre, science museums and even a railroad museum. Free concerts are offered frequently. Another popular attraction is the SeaWorld, a 190-acre marine park.

San Diego’s varied attractions, as well as its business climate, offer many opportunities for students to explore the local culture, meet people from around the world, and gain business experience. At San Diego State University, for example, students in the American Language Institute’s study tour program learn English both in the classroom and while sightseeing.

3 . The Silk Road is arguably the most famous lung-distance trade route of the ancient world. This passage connected Europe in the West with China in the East, and allowed the exchange of goods, technology, and ideas between the two civilizations. Although merchants could make huge profit travelling the road, it was not without risk.

The main Silk Road started in Chang’an (known today as Xi’an), the early Han capital. Travelers commencing their journey from this city could take a northern route that would take them across China’s northwestern provinces. After this, they would face the Gobi Desert, arguably the greatest danger of the Silk Road.

The Gobi Desert, the largest desert in Asia, consists-mainly of rocky, hard earth. This feature made it easier for traders to travel across, compared to sandy deserts like the neighboring Taklamakan Desert. Like other deserts, the Gobi Desert is dry and hot, and therefore the biggest challenge travelers faced was obtaining enough water for themselves as well as for their camels.

So, rest stops were created along the route, allowing travelers to rest, cat and drink. These places also promoted the exchange of goods, and even ideas, amongst the travelers who stopped there. Usually, the rest stops were placed within a day’s journey of each other. In this way, travelers could avoid spending too much time in the desert, which would make them targets for robbers, another danger of the Silk Road.

Once through the Gobi Desert, travelers would continue their journey into Iran, Turkey, and finally Europe. Whilst this part of the journey may have been less dangerous, it is not entirely without its perils.

For those looking to escape the concrete jungle, maybe it’s time to dive into the bamboo forests of southern Sichuan.

A natural forest that people in Sichuan province tend     1     (visit) is the Southern Sichuan Bamboo Sea in Yibin. The 120-square-kilometer Bamboo Sea is the     2     (large) bamboo park in China and its average temperature seldom drops below zero degrees Celsius in winter     3     many parts of the country are covered with snow and ice.

Known as one of the country’s 10 most beautiful forests, it     4     (be) a popular tourist attraction since the Oscar-winning Crouching Tiger Hidden Dragon     5     (shoot) there in 2001.

Two years later, the bamboo forest received world-wide     6     (recognize) as a bamboo reserve in December 2003,     7     (become) the fourth tourism destination in China to be granted Green Globe 21 certification.

The Bamboo Sea covers Changning and Jiang’an, two counties under the authority of Yibin. Amazed at its vast expanse (浩瀚), Huang Tingjian,     8     poet from the Song Dynasty, described it     9     “bamboo waves”. As Huang was an     10     (influence) man, his description gave rise to the forest’s popular nickname-the Bamboo Sea.

10 . If you’ve ever worried that we’ve solved all the mysteries of nature, fear not. Minnesota’s Devil’s Kettle Falls has been attracting hikers and geologists for generations. At the falls, along Lake Superior’s North shore, a river forks at a rock outcrop. While one side runs down a two-step stone bank and continues on like a normal waterfall, the other side falls into a deep hole and disappears apparently forever.

And this baffling situation only gets strange when geologists start explaining Devil’s Kettle (水壶). Consider, for instance, the sheer quantity of water pouring into the kettle every minute of every day. While the idea of some kind of broad, underground river is an exciting device in movies, the reality is that those sorts of deep caves are rare.

Another idea is that millions of years ago, a hollow lava tube may have formed beneath the falls, in the subsurface layer of rock. Over time, the theory suggests, the falling water eroded (侵蚀) the surface and fell straight down into the ancient lava tube, providing wide-open access to the floor of Lake Superior. Again, there are problems with this theory, because no lava tubes have ever been found in any of the hundreds of exposed rock beds in the area.

In February 2017, scientists said that water that disappears into the rock at Devil’s Kettle rises again in the stream below the falls. To confirm the theory, scientists plan on conducting a dye trace during a low-water flow period. They’ll pour a vegetable-based dye into the pothole and watch where the dye comes to the surface again.

“What we think is happening is that the water is going in the kettle, and coming up pretty close to immediately downstream of the falls,” Green said.

Green admits that if the dye is found below the falls like the scientists suspect, then much of the Devil’s Kettle Falls mystery will be gone. “Were there a little bit of that,” he said, “the folks would not be going to stand there and wonder. But it will still be a fascinating spot, and a beautiful spot.”