Ok so the sentence should be:

Она расположена в одном из самых дешёвых районов Москвы. (and it means)
It is situated in one of the very cheapest neighbourhoods in Moscow.

and the sentence is fine as long as it refers to a feminine noun. It could refer to a church (церковь) or a school (школа) for example, since they are feminine nouns.



By the way, what are some cheap neighbourhoods of Moscow, out of interest? Are such neighbourhoods dangerous?