2Is it just me, or should hill and valley be taken to be (possibly) plural? I read "over hill and valley" as a kind of summary, where it could be translated to "over at least one hill and at least one valley". – colllin – 2015-11-19T16:12:13.967

3I think "over hill and valley" is idiomatic and metaphorical here. It does not mean literally one hill and one valley, just a way of describing terrain. – stangdon – 2015-11-19T17:44:17.257

4A similar idiom is "over hill and dale" which just means traveling through varying terrain, often walking. – mkennedy – 2015-11-19T20:24:27.357

1I agree with @colllin, this is just a fancy/poetic way to say over hill[s] and valley[s]. It doesn't (and can't) mean one specific hill or valley. Colllin's 'translation' is right. (And I think the OP's real confusion is coming from the lack of any article for hill and valley, but I might be wrong.) – Numeri says Reinstate Monica – 2015-11-19T22:13:14.040

I don't see across here....It seems to me to mean "I walked all over hills and valleys..." like "there's paper all over the floor." Am I totally wrong on this? Is my interpretation a possibility? – None – 2015-11-19T22:47:12.403

18906335678, Across also means from one side to the other of something. He walked across the road. – Khan – 2015-11-20T02:25:39.213

@8906335678 - "Over" just means "across a barrier or intervening space". It does not mean the same thing as "all over", so no, a native speaker would not interpret it that way.

http://www.learnersdictionary.com/definition/across – Khan – 2015-11-20T16:08:51.147

http://dictionary.cambridge.org/dictionary/english/across – Khan – 2015-11-20T16:10:11.887