The Leaning Tower of Pisa was straight like a pole when the construction began in 1173. It started to shift direction soon after construction because of poor foundation in addition to the loose layer of subsoil(底土). At the beginning, it leaned to the southeast before the shaky foundation started to shift leaning towards the southwest. After the period of structural strengthening at the beginning of the 21^st century, now the Leaning Tower of Pisa leans at an angle of 3.97 degrees.

    In 1178, the shift in direction was observed for the first time when the construction had progressed further to the third floor. The tower was heavy for the three-meter foundation that was built on a weak area of land.

    For compensating(补偿) the leaning position, the builders started to construct the upper floors with one side higher than the other one. This caused the tower to lean in the other direction. This unusual structure led to the tower being actually curved. In spite of these efforts, the tower kept on leaning.

    The government of Italy started to plan prevention of the complete collapse of the tower in 1964. However, a request was put forward by the authorities to keep the leaning position because of the tourism industry of the region.

    After nearly two decades of careful planning by engineers, historians and mathematicians, the stabilization efforts for the Leaning Tower of Pisa started in 1990. The tower was closed for the general public and the people living nearby moved away. For reducing the total weight of the tower, its seven bells which represented the seven musical notes were removed. The tower was reopened for the general public on December 15, 2001.

    In May 2008, after removing another 70 metric tons of earth, the engineers announced that the tower had been finally stabilized and it would remain stable for at least 200 years.

    If you're new to San Francisco, paying the city a visit, or simply looking for a new playground for you and your dog, here are four of the finest dog parks in San Francisco.

    Corona Heights Dog Park

    Often visited by residents from all over the city because of its nearness to the Randall Museum, Corona Heights Dog Park offers pets and owners breathtaking view after a steep hillside climb, and a fenced dog area that allows dogs to let loose without a leash（狗链）. Owners will also enjoy the playground, tennis courts and basketball courts.

    Dolores Dog Park

    The grounds of Dolores Park once served as camps for those who were left homeless by the 1906 earthquake, but now are often visited by crowds of Mission District people. Four-legged friends can also wander about carefree off-leash while making friends with other members of the doggie community.

    Pine Lake Dog Park

    Famous for its place as a rest stop for hundreds of species of birds to fly to and from warmer climates, Pine Lake Park is also prized by city dogs and their owners for their nice hiking paths, picturesque lake suited for swimming, and off-leash area on the park's west end that lets dogs run free.

    Buena Vista Dog Park

    With a history of 146 years, Buena Vista Park is San Francisco's oldest park. Dogs and owners with plus energy will love burning it on this park's steep paths and winding staircases. Dog owners should have good control over their dogs, as it's quite easy for dogs to get separated when going through Buena Vista's many twists and turns.

    There's been a lot of talking about white-and-blue collar workers, and you may have even heard of gold collar workers, but lately a new color of collar is making its way into China's urban vernacular(土话)—green. Green collars say no when work is life and life is work. They choose to get out of the fast lane(车道), and explore new ways of living "green".

    Living green doesn't mean someone is working as an environmentalist, biologist or scientist. Instead it is more of a lifestyle choice. A typical green collar is well educated like a white-collar but physically tough like a blue-collar, likely born in the 70s or 80s of the last century and living in one of China's big cities, with a monthly income well above 5,000 yuan(about US $700).

    The life of a green collar may go something like this: Turn off the mobile phone after work, eat only healthy food rich in vitamins, go on hikes every weekend, and like to help the underprivileged.

    Green collars even have their own club. In Beijing, the Green Collar Club is for people who share a "be happy, healthy and helpful" spirit. The club often holds charity parties and uses the donations for environmental protection and poverty relief(摆脱贫困) projects in China.

    "They are successful in their careers, but do not miss the pleasures in life. They have a lot of money, but do not fall slave to it." said Zuo Shiguang, one of the founding members of the club.

    Bad news sells. If it bleeds, it leads. No news is good news, and good news is no news. Those are the classic rules for the evening broadcasts and the morning papers. But now that information is being spread and monitored in different ways, researchers are discovering new rules. By tracking people's e-mails and online posts, scientists have found that good news can spread faster and farther than disasters and sob stories.

    "The 'if it bleeds' rule works for mass media," says Jonah Berger, a scholar at the University of Pennsylvania. They want your eyeballs and don't care how you're feeling. But when you share a story with your friends, you care a lot more how they react. You don't want them to think of you as a Debbie Downer."

    Researchers analyzing word-of-mouth communication—e-mails, Web posts and reviews, face-to-face conversations—found that it tended to be more positive than negative, but that didn't necessarily mean people preferred positive news. Was positive news shared more often simply because people experienced more good things than bad things? To test for that possibility, Dr. Berger looked at how people spread a particular set of news stories: thousands of articles on The New York Times' website. He and a Penn colleague analyzed the "most e-mailed" list for six months. One of his first findings was that articles in the science section were much more likely to make the list than non-science articles. He found that science amazed tines' readers and made them want to share this positive feeling with others.

    Readers also tended to share articles that were exciting or funny, or that inspired negative feelings like anger or anxiety, but not articles that left them merely sad. They needed to be aroused one way or the other, and they preferred good news to bad. The more positive an article, the more likely it was to be shared, as Dr. Berger explains in his new book, "Contagious: Why Things Catch on."

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A casual walk along the Beijing Central Axis, connecting the Drum Tower and the impressive Forbidden City — this was Zhao's first city-walking journey in the spring of last year. Since then, the 21-year-old student from Beijing Foreign Studies University has remained a city-walk fan, believing it to be the best way to "rediscover a city". 

"I visited Beijing before the start of my college life here, and it was a typical package tour during which going to scenic spots and taking photos was a big thing. The crowded tourist attractions gave me the impression that Beijing was a noisy place," Zhao said. 

With the increasing variety of travel choices, traditional group tours no longer satisfy people who are looking for a more personal and different travel experience and hoping to explore every part of the city in a more immersive （沉浸式的） way. 

Compared with tightly scheduled routes （路线） and picture-taking tours, city-walking focuses on free, casual and spontaneous （自发的） experiences. The trending city-walk culture, which encourages experiencing urban life with no transportation means except one's legs and feet, has also made splashes on various social media platforms. 

On the video-sharing app Douyin, the Chinese version of Tik-Tok, a recent video about citywalk routes in Guangzhou, Guangdong province, has gained more than 171,000 likes, with 72,000 viewers of all ages adding the video to their favorites. According to a report from lifestyle-sharing platform Xiaohongshu, in the first half of this year, searches about city-walks increased 30-fold from the previous year. "The route offers a glimpse （瞥见） into the culture and landscape in different historical stages, as well as its beautiful natural scenery," it said. 

Following his experience in Beijing, Zhao has also explored Wuhan in Hubei province, Hangzhou in Zhejiang province and other cities through city-walking tours. "City-walking is all about doing whatever you want in your own exploration of a city, and it is actually the kind of slow-paced, low-carbon lifestyle that I relate to so much," he said.