أنحاء المدينة جميلة.

This is a nominal sentence in Arabic.

• أنحاء المدينة = the subject
• جميلة = the predicate

In present-tense Arabic, the verb to be is usually not written or spoken. So Arabic says literally:

• أنحاء المدينة جميلة
• word-for-word: the areas of the city beautiful

But in natural English, that becomes The areas of the city are beautiful.

Because أنحاءُ المدينةِ is the subject of the nominal sentence, and the subject of a nominal sentence is normally nominative.

So in full vocalization, you get:

• أَنْحاءُ = nominative
• المدينةِ = genitive
• جميلةٌ = nominative

The full form is:

• أَنْحاءُ المدينةِ جميلةٌ

It is an iḍāfa construction, often called a construct phrase.

Structure:

• أنحاء = first noun (muḍāf)
• المدينة = second noun (muḍāf ilayhi)

Together they mean:

• the areas of the city
• the parts of the city

This is one of the most common ways Arabic expresses of.

So instead of saying areas of the city with a separate word for of, Arabic simply puts the two nouns together:

• أنحاء المدينة

Because in an iḍāfa, the first noun normally does not take الـ.

So Arabic says:

• أنحاء المدينة

not:

• الأنحاء المدينة

Even though أنحاء has no الـ, the whole phrase is still definite, because the second noun المدينة is definite.

So:

• أنحاء المدينة = the areas of the city

Also, the first noun in an iḍāfa normally does not take tanwīn either.

Because it is the second term of the iḍāfa (muḍāf ilayhi), and that noun is normally genitive.

So:

• المدينةِ ends with a kasra in full vocalization

This is true very generally in Arabic:

• بابُ البيتِ = the door of the house
• مركزُ المدينةِ = the center of the city
• أنحاءُ المدينةِ = the areas of the city

This is a very important Arabic rule:

Non-human plurals are usually treated grammatically as feminine singular when adjectives or predicates agree with them.

So although أنحاء is plural in meaning, Arabic uses:

• جميلة
  not:
• جميلات
• جميلون

That is why the sentence is:

• أنحاء المدينة جميلة

Compare:

• البيوت كبيرة = The houses are big
• الأشجار طويلة = The trees are tall

Even though houses and trees are plural, the adjective is feminine singular.

Because it is the predicate of the sentence, and predicates in simple nominal sentences are often indefinite.

So:

• أنحاء المدينة جميلةٌ = The areas of the city are beautiful

Here جميلةٌ is simply describing the subject.

If you added الـ and said الجميلة, it would usually no longer sound like the normal predicate beautiful. It would suggest something more like the beautiful one, which is not what this sentence is doing.

Fully vowelled, it is:

• أَنْحاءُ الْمَدِينَةِ جَمِيلَةٌ

A careful MSA pronunciation would be approximately:

• anḥāʾu l-madīnati jamīlatun

A few useful notes:

• The final hamza in أنحاء is pronounced.
• المدينةِ has a genitive ending because it is the second noun in the iḍāfa.
• جميلةٌ has a nominative ending because it is the predicate.

If you pause at the end, the final short vowel is usually not pronounced, so جميلةٌ is heard as jamīlah.

أنحاء is a plural, specifically a broken plural.

Its dictionary singular is:

• نَحْو

In this kind of sentence, أنحاء means something like:

• areas
• parts
• regions
• aspects

For learners, the important thing is simply to recognize أنحاء as a plural noun meaning areas/parts. Its singular is not very transparent from the plural, which is normal with broken plurals.

Not by itself in this sentence.

Here, أنحاء المدينة is a noun phrase meaning:

• the areas of the city
• the parts of the city

If you want the meaning throughout the city or in different parts of the city, Arabic usually uses a preposition, especially:

• في أنحاء المدينة = throughout the city / in the different parts of the city

So:

• أنحاء المدينة جميلة = The areas of the city are beautiful
• في أنحاء المدينة = throughout the city

That distinction is very useful to notice.