In the fall, many Japanese people enjoy viewing the colorful autumn leaves in parks, forests or mountains. Viewing autumn leaves is called hunting of red leaves or momijigari. It is said that a sudden change of air temperature from warm to cold in fall makes beautiful autumn leaves. In the fall, colorful forests and mountains enthrall many people, and they are willing to travel to famous autumn leave viewing spots. Some people also enjoy hiking in such places, while others may enjoy having meals under trees whose leaves have just turned into red or yellow. So, momijigari may include hiking or picnics. Fall is also the season for hiking and climbing. There are many places for such in Japan, since sixty percent of the Japanese archipelago is mountainous. It is said that hiking and climbing are very popular among the middle-aged and retired people in Japan in the fall.