Thousands of athletes gather every four years to compete in this international extravaganza that alternates between the Summer Games and the Winter Games. The modern Olympics began just before the 20th century and are a revival of games that originated in Greece. The games include numerous symbols and rituals — notably the torch, the flag and the opening and closing ceremonies. There has been some controversy in recent years over the environmental impact of the Olympics, but the spectacle and athleticism of the Games make it an internationally uniting event. (Photo: Flickr)

London Olympics go for environmental gold

Big Snapshot: Divers test the waters, vie for Olympic berth

MNN's week in review: Olympic venues and a beauty regimen for 2012

Snowboarder's remarkable return to the slopes

2012 Olympic Games: London unveils venues

Big Snapshot: Pan American Games

Big Snapshot: Testing the 2012 London Olympics venues

Olympian Jeret 'Speedy' Peterson commits suicide, police say

Olympic hopeful Sally Meyerhoff killed in cycling accident

Iran sees Zionist conspiracy in Olympic logo

Go for the green! Olympic athletes push for climate change action

Sochi 2014: An ecological disaster?