The moon rising above the Forth Rail Bridge in The Firth of Forth from North Queensferry, England on July 16, 2019. (Photo by South West News Service)

Heavy equipment works along the still under construction Bamiyan-Yakawlang road June 10, 2011 in Yakawlang, Afghanistan. The 69 Million US$ project is supported by the Government of Japan and World Bank. The 90K road project was started three years ago and is slated to be finished within another year. This new road means faster travel from Bamiyan to Afghanistan's only national park, Band-e-Amir. This is in of the safest parts of the country and the hope is to expand tourism in the region. (Photo by Paula Bronstein/Getty Images)

The Y-40 Deep Joy is the worlds deepest pool. Y-40 is projected by Architect Emanuele Boaretto and supported by the “Boaretto Group Hotel and Resort”. The name Y-40 is inspired by mathematical symbols. “Y” is the ordinate axis of the Cartesian system and “–40” means the world's record depth or our pool- that is 40 meters underground. (Photo by Courtesy Y40 Deep Joy)

Salar de Uyuni (or Salar de Tunupa) is the world's largest salt flat at 10,582 square kilometers (4,086 sq mi). It is located in the Potosí and Oruro departments in southwest Bolivia, near the crest of the Andes, and is elevated 3,656 meters (11,995 ft) above mean sea level. The Salar was formed as a result of transformations between several prehistoric lakes. It is covered by a few meters of salt crust, which has an extraordinary flatness with the average altitude variations within one meter over the entire area of the Salar.

Natalia Arango works with her mine detector in a zone of landmines planted by rebels groups near Sonson in Antioquia province, November 19, 2015. Women's work takes on a nontraditional meaning for fifteen Colombian women who work to rid the Antioquia Mountains of deadly landmines as the country edges closer to a peace agreement with Marxist rebels to end over a decade of conflict which has claimed 220,000 lives. (Photo by Fredy Builes/Reuters)

Chocolate is the greatest gift the Earth has given us. The dessert table would be a sad sight without it. It’s so beloved, so appreciated, that the Swedish scientist who named the cocoa plant that gives us chocolate called it Theobroma cacao, which means “food of the gods”. Here: Farmer holding a freshly cut cocoa bean pod, revealing the pulp and seed inside on a rainforest farm. (Photo by Doug McKinlay/Getty Images)

Everyone wants to get something for nothing - whether it's a lucky upgrade that means you can turn left when you get on a plane instead or heading off into the economy seats, or even getting a few extra features thrown in for free when you buy a new car.

As some of the sharpest businesses around, no-one understands this quite as well as casinos and that's why they all have a system that they call comps. It's short for "complimentary offers" and these are special treats specially designed to reward you for your loyalty to the casino in question. They're basically bonuses.

People walk on a sightseeing platform in Zhangjiajie, Hunan Province, China, August 1, 2016. China has opened a 100-metre-long glass skywalk stretching around a cliff on the side of the Tianmen Mountain. The skywalk provides a view of a 300-metre drop and overlooks Tongtian Avenue, a mountain road with 99 turns that snakes up the mountain. When translated in English, it means “Avenue to the Sky”. (Photo by Reuters/Stringer)