Small transportation boats, known as bumboats, leave trails of light as they travel across Marina Bay past the skyline of Singapore in this photo taken in 2004. Singapore holds a Jubilee weekend from 7 to 10 August to celebrate the 50th anniversary of its independence. Fifty years ago, hundreds of small boats lined the Singapore river in the city centre. Today, most small boats are gone, except a handful of neon-lit tourist ferries. Maritime trade is still the backbone of the city-state but after decades of rapid growth Singapore, which at less than half the size of London is among the world’s most densely populated nations, is also a popular tourist destination and a thriving global financial hub. (Photo by Edgar Su/Reuters)

Thai emergency staff help the injured after the scene of an explosion near Erawan Shrine, central Bangkok, Thailand, 17 August 2015. An explosion in a busy commercial district in the Thai capital killed at least 15 people. Witnesses said the explosion happened around 7:15 pm (12:15 GMT) at the Rajprasong Intersection, a business area famous among tourists and locals for a revered Hindu shrine. (Photo by EPA/Stringer)

A tour group wanders through block 7 of Eastern State Penitentiary in Philadelphia, Pennsylvania April 30, 2014. Opened in 1829, with the original corrective system of “confinement in solitude with labor”, the penitentiary housed about 75,000 inmates in its 142 years of operation. At Eastern State reunions, former inmates, staff and guard gather to share memories and trade stories and get a chance to describe their experiences in question-and-answer sessions with the public. (Photo by Mark Makela/Reuters)

Visitors walk past the fully equipped dining table inside the “Crazy House”, which is completely built upside-down, in the village of Affoldern near the Edersee lake, May 7, 2014. Three friends came up with the idea to build the tourist attraction, which cost about 200,000 euros and took some six weeks to complete. (Photo by Kai Pfaffenbach/Reuters)

Revellers continue to party and dance through the night and day during the second day of the San Fermin Running Of The Bulls festival, on July 7, 2014 in Pamplona, Spain. The annual Fiesta de San Fermin, made famous by the 1926 novel of US writer Ernest Hemmingway “The Sun Also Rises”, involves the running of the bulls through the historic heart of Pamplona. (Photo by Christopher Furlong/Getty Images)

Park Ji-soo of South Korea performs her contemporary variation during the final of the 43rd Prix de Lausanne at the Beaulieu Theatre in Lausanne February 7, 2015. The Prix de Lausanne is an annual international dance competition for dancers aged 15 to 18. A total of 67 participants from 18 countries were selected from 300 applicants to take part in this year's week-long competition, from which the jury has shortlisted 20 finalists to compete for Saturday's finals. Six of this year's finalists will be awarded a one-year all expenses paid scholarship at one of the Prix de Lausanne's partner schools or companies, among the most prestigious in the world. (Photo by Denis Balibouse/Reuters)

Actress with the Donbass Opera Theatre prepares to perform Eugene Onegin in Donetsk, Ukraine, Saturday, February 7, 2015. For the few dozen spectators that turn up, the weekly performances at the city's opera house serve as a respite from the war raging outside between Russian-backed separatists and Ukrainian government forces. (Photo by Petr David Josek/AP Photo)