French language Q&A Forum

Fun exercise. I enjoyed it a lot, especially imaging myself walking on the beach, naked toes in the warm sand!

Just one simple question:

I am familiar with the expression, "a la montagne", as in "aller a la montagne". And, j'adore "la montagne".  

But I have also heard "les montagnes" in phrases such as "L'ete, je marche dans les montagnes." 

I have reviewed the lesson on singular/plural (collective nouns): "les cheveux"; "les toilettes"; "la police" etc. There is no mention of "la/les montagnes".

I would very much appreciate an explanation of when to use the singular, "la montagne" vs. the plural, "les montagnes." 

Merci beaucoup !