What is the difference between "산 속" and "숲 속"?
I am reading "언어 학습자를 위한 한국 전래동화".
It says that:
산 속을 걷고 있었습니다 means "walking in the forest"
숲 속을 걷고 있었습니다 also means "walking in the forest"
Is there any difference?

Question

What is the difference between "산 속" and "숲 속"?
I am reading "언어 학습자를 위한 한국 전래동화". 
It says that:
산 속을 걷고 있었습니다  means "walking in the forest"
숲 속을 걷고 있었습니다 also means "walking in the forest"
 Is there any difference?

Answer

산 속 = in the mountains

숲 속 = in the forest

Answer

*I would add -을 after 숲 속, so, it should read 숲 속을 걷고 있었습니다.