Throughout the world humans have preserved the dead and mummified them for different reasons, depending on their beliefs. However there are also a number of mummies preserved by incidental exposure to elements, or extreme coldness, such as ice mummies. The most famous incidental mummy (also called "natural mummy) is Ötzi the Iceman.
Ötzi was discovered in 1991, in a glacier in the Ötztal Alps, hence the nickname. He has been dated to 3300 BC.