Please, see this related question for more context.
Thank you very much.
In this particular case, both この自然が多い町 and 自然が多いこの町 refer to the same thing, and they are interchangeable.
In many other cases, however, placing この at a distant place may introduce a difference in meaning:
この自然 ("this nature") is not something we commonly say, so when we hear この自然が多い町, we usually assume この modifies 町 rather than 自然.
In general, unlike English, Japanese is a rather strictly head-final language. That is, if there are two or more modifiers for a single word, they all have to come before the modified word, and you may have to determine which is modifying which solely by context. Japanese people learn how to avoid confusion by intuition, but it may seem hard to learners at first. Basically it's usually safer to place a short modifier like この as closely as possible to the modified word. See this for longer discussion: Are Japanese modifiers "greedy", "anti-greedy", or do they mean whatever people choose them to mean?