Relative clauses with になる and のなる


I self study Japanese and among the things I do is reading easy NHK news
articles.

[Here is one article I
read.](http://www3.nhk.or.jp/news/easy/k10010062131000/k10010062131000.html)
In the article appears the word 首都 _capital city_. Hovering over it would give
the following sentence:

> その国の議会や中心になる役所のある都市

If I am not mistaken this sentence should mean something along the lines of:

> City with a public office becomes the capital and the center of the country.

Now, whether the above translation is correct or not, I have not idea how this
sentence works, I can't wrap my head around it. I understand each part (word,
particle, verb, etc.) separately (to a certain degree for I can't understand
this sentence) but, I can't understand how those individual parts integrate
and form this sentence.

With that said I would like to receive your help with translating this
sentence and helping me understand it, the sentence structure, word order,
grammar and any other thing that would help me understand the sentence and how
it was created.

Unless you have to please refrain from using rōmaji in your answers.




You should read the sentence in this way:

[code]

    NP{ 
      NP(その国) POSS(の) NP[ NP(議会) 
                              AND(や) 
                              NP(中心になる役所) ] } 
    SUBJ(の) 
    V(ある) 
    NP(都市)
    
[/code]

, where NP{} is the subject of the sentence modifying 'city'. It's not a full
parse, but I hope you understand the point here.

OP seems to have a problem reading NP[], which is a simple conjunction of two
noun phrases: 'parliament' and '中心になる役所'. You should note that (に)なる here does
not mean 'becoming', it's more like 'playing a role of'. So 中心になる役所 translates
into 'government offices playing central roles' or more naturally 'important
public offices'.

