In general a "rinconada" is an incoming angle formed at the intersection of two houses, two streets, or two roads.
In geography a "rinconada" is the land between two mountain branches.
In the next image I tried to do a draw of it, the spiral shows the place that I’m referring to, where some houses could be settled, for example.
UPDATE: I take the image shared by @Mari-LouA where I mark in red what is the closest place to what I’m asking for, and I have added the translation for "gully": quebrada
In Appalachia, where I grew up, we referred to a smallish valley (hollowed out area) in a mountain range (not down at the bottom of the mountain but between two taller areas which is what the illustration looks like)as a "hollow" which we pronounced "holler". People settled in hollows because they generally had creeks in them (were probably formed by creeks, actually) and were somewhat protected from the elements, and consequently towns grew up there.
So, country singer Loretta Lynn’s famous tune says that she was born in "Butcher Holler", which is a town in Kentucky (technically Butcher Hollow, KY).
The problem with offering this word as a translation is, in my experience, people don’t use it much in conversation any more. It’s found more in place names now. We are more likely to say "5 miles south on Hwy 70" if we are referring to a geographic location. But if you used this term in my region, we would certainly know what you meant.
Another option might be "cut", which is a passage between two taller areas in a mountain range