Switzerland has never hosted the Summer Olympics. It has hosted the Winter Olympics twice, in 1928 and 1948. In both cases it was hosted in St. Moritz.
Torino never hosted the Summer Olympics. They did, however, host the 2006 winter Olympics.
The host city of the 2016 Summer Olympics is Rio de Janeiro, Brazil.
London was the host city for the 2012 Summer Olympics.
1920 Summer: Antwerp, Belgium1920 Winter: None - The first Winter Olympics was not until 1924.1924 Summer: Paris, France1924 Winter: Chamonix, France1928 Summer: Amsterdam, Netherlands1928 Winter: St. Moritz, Switzerland
London will host the 2012 Olympics
Torino has not hosted the Summer Olympics. They hosted the Winter Olympics in 2006.
South Korea has not hosted the Winter Olympics. Seoul did host the 1988 Summer Olympics.
Rio de Janeiro Brazil will be the host city of the 2016 Summer Olympics. The only 2012 Olympics will be the London 2012 Summer Olympics
Melbourne hosted the 1956 Summer Olympics.
England
For the 2016 Summer Olympics, Chicago is a candidate for the host city. The 2014 Winter Olympics will be in Sochi, Russia. The 2012 Olympics will be in London, and the 2010 Winter Olympics will be held in Vancouver, Canada.