northern mountains; mountains to the north
Refers to mountains located in the north, often used in geographical descriptions or place names.
There is still snow on the northern mountains.
The mountains to the north of this town are famous for their autumn leaves.
北山 refers to mountains in the north while 南山 refers to mountains in the south, the direct directional opposite.
Compound of 北 (north) and 山 (mountain). The reading きたやま is a straightforward kun'yomi combination.