valley

laakso An elongated depression between hills or mountains, often with a river flowing through it.
{{quote-magazine|date=2013-08-16|author=http://www.theguardian.com/profile/johnvidal John Vidal
The area which drains into a river.
Any structure resembling one, e.g., the meeting point of two pitched roofs.
The internal angle formed by the intersection of two sloping roof planes.