Among the mountains is deep valley. The vast stream run off from the mountains above trap a layer of moisture along with the heat accumulated by day to create a tropical zone, filled with lush, jungle like plants. During the day the whole of the valley enjoys this atmosphere, however heat inversion ensures that nights within the very base are cold, while the upper reaches remain hot. As such, the base of the valley hosts more deciduous plant life. This area is popular with plant pokèmon and tropical species, though they do tend to stick to the upper reaches of the valley at night.