Photographer Andy Hall joins the thousands of fans from west Africa who have gathered for Baaba Maal's annual Blues du Fleuve festival in Senegal. Here: Dancers wait to perform on stage. (Photo by Andy Hall/The Observer)

A passenger not wearing pants sits in a subway train during the “No Pants Subway Ride” in Prague, Czech Republic, January 10, 2016. The event is an annual flash mob and occurs in different cities around the world in January, according to its organisers. (Photo by David W. Cerny/Reuters)

Run by the Society of German Nature Photographers (Gesellschaft Deutscher Tierfotografen), the prestigious annual contest celebrates the best wildlife photography from members in Germany. Here: Landscapes, second place: Florian Smit, “Rainforest” (Danum valley, Borneo). (Photo by Florian Smit/2019 GDT Nature Photographer of the Year)

Samburu tribesmen stand during the Maralal Camel Derby, Kenya, August 15, 2015. Maralal, a small, arid town about an eight-hour drive north of the Kenyan capital Nairobi, holds an annual camel festival, bringing together members of the Samburu, Turkana and Pokot semi-nomadic cattle-herding tribes. (Photo by Goran Tomasevic/Reuters)

Cass Gilmore harvests cranberries in a bog at Gilmore Cranberry Company in Carver, Massachusetts September 14, 2015, the beginning of the cranberry harvesting season. According to the Cape Cod Cranberry Growers' Association, 200,000,000 pounds of cranberries are grown annually in Massachusetts. (Photo by Brian Snyder/Reuters)

Participants stretch their bodies as they pose for pictures before the Beijing International Marathon in Beijing, China, September 20, 2015. About 30,000 runners participated in the annual running event. (Photo by Kim Kyung-Hoon/Reuters)

Vivid Sydney is a unique annual event of light, music and ideas, featuring an outdoor 'gallery' of extraordinary lighting sculptures, a cutting-edge contemporary music program, some of the world's most important creative industry forums and, of course, the spectacular illumination of the Sydney Opera House sails. It positions Sydney as the creative hub of Australia and the Asia-Pacific region, and delivers both innovative live entertainment and creative inspiration on a grand scale.

The Chicago Air & Water Show is an annual air show held on the shore of Lake Michigan in Chicago, Illinois. The show has been held each year since 1959 and is Chicago's second most popular festival. In 2005, 2,200,000 watched the Chicago Air and Water Show.