hi bluppfisk,

This sentence is a bit long and confusing because of the clause, so in that case, it would be better to split the sentence in two and connect them with "starting from there".

So you could say "我在离北京市区不到30公里的团结镇发现了一家青年旅社，你可以从那开始去探索附近的山谷" and the second part could be"从那(开始)，你可以(一路)去附近的山谷里探索" which would sound more native.

There's a book called (现代汉语生成语法 - "A Generative Grammar of Mandarin Chinese") which may help with attributive clauses. Hope it helps. :)

- Grace