Esa región del norte tiene una sierra muy bonita y una llanura enorme al mismo tiempo.

These are all demonstratives:

• esta = this
• esa = that
• aquella = that over there / that one farther away

So esa región means that region.
Spanish often chooses among these based on how psychologically or physically close something feels to the speaker.

Also, región is a feminine singular noun, so the demonstrative has to match it:

• esta región
• esa región
• aquella región

Not ese región.

Because de + el contracts to del in Spanish.

So:

• de + el norte → del norte

This is a standard contraction, just like:

• a + el → al

Examples:

• la capital del país
• al mismo tiempo

Important: this contraction happens with el the article, but not with Él meaning he.

Here, del norte means in the north or from the northern part depending on context.

In esa región del norte, it describes which region we mean: that region in the north / that northern region.

It is a very natural Spanish way to identify location:

• una ciudad del sur = a city in the south
• un pueblo del interior = a town inland
• la costa del este = the east coast

So del norte is functioning like a descriptive phrase attached to región.

Yes. Spanish uses tener very naturally to talk about the features of a place.

So:

• La ciudad tiene muchos parques = The city has many parks
• La casa tiene tres habitaciones = The house has three rooms
• La región tiene una sierra = The region has a mountain range

In English, we might also say there is or it contains, but in Spanish tener is completely normal here.

In this sentence, sierra means mountain range.

That can confuse learners because sierra can also mean saw as a tool. The meaning depends on context.

Here, because the sentence is describing geography, una sierra muy bonita clearly means a very beautiful mountain range.

Related words:

• montaña = mountain
• cordillera = mountain range, often a larger or more formal term
• sierra = mountain range, often rugged or smaller than a major cordillera

Llanura is a noun meaning plain or flat lowland area.

So:

• una llanura enorme = an enormous plain

By contrast, plano/plana is usually an adjective meaning flat:

• una zona plana = a flat area

So if you want the geographical feature itself, you use llanura.
If you just want to describe something as flat, you often use plano/plana.

Because both sierra and llanura are countable feminine singular nouns.

So each one needs its own article:

• una sierra
• una llanura

Spanish does not usually omit the second article in this kind of structure.

Also, the article matches the noun’s gender:

• una sierra because sierra is feminine
• una llanura because llanura is feminine

Because in Spanish, adjectives often come after the noun.

So:

• una sierra bonita
• una llanura enorme

This is the most neutral, common order for many descriptive adjectives.

Spanish can sometimes place adjectives before the noun, but that often changes the tone, emphasis, or style. For a straightforward description, post-noun placement is normal.

So this sentence sounds natural and unmarked.

Because muy bonita means very beautiful, and that is a totally normal combination.

With enorme, Spanish often treats it as already a strong adjective, so una llanura enorme sounds natural by itself.

You can say muy enorme in some contexts, but it is less standard and can sound exaggerated or stylistic. Native speakers are more likely to say:

• enorme
• muy grande
• inmensa
• gigantesca

So in this sentence, enorme alone already gives strong emphasis.

Yes, al mismo tiempo is a very common expression meaning:

• at the same time
• simultaneously

It is made up of:

• a + el → al
• mismo = same
• tiempo = time

In this sentence, it means the region has both features simultaneously: a mountain range and a plain.

It is a fixed, very natural phrase in Spanish.

In most of Spain, ll is pronounced the same as y for many speakers. This is called yeísmo.

So llanura is usually pronounced roughly like:

• ya-noo-ra

More carefully, something close to lya-noo-ra may be heard in some speakers or regions, but for most learners of modern Spain Spanish, treating ll like y is fine.

Also:

• llanura has stress on -nu-
• the final r is a light tapped Spanish r

Because the stress falls on the last syllable: re-gión.

In Spanish, a word ending in n, s, or a vowel is normally stressed on the second-to-last syllable unless an accent mark shows otherwise.

Without the accent, region would be expected to sound wrong according to Spanish stress rules. The written accent tells you the correct stress is:

• re-GIÓN

This is useful both for pronunciation and spelling.

Sometimes yes, but the structure would change.

Original:

• Esa región del norte tiene una sierra muy bonita y una llanura enorme al mismo tiempo.

Possible alternative:

• En esa región del norte hay una sierra muy bonita y una llanura enorme.

Difference:

• tiene = the region has these features
• hay = there is/are these features in that region

Both are natural, but tiene presents the region almost like a whole possessing those characteristics, while hay focuses more on existence.

Bonita often means pretty, nice, or beautiful, depending on context.

For landscapes and places, muy bonita can absolutely be translated as very beautiful or very pretty.

Compared with hermosa or preciosa, bonita is often a bit more everyday and less dramatic, but it is still very positive.

So una sierra muy bonita sounds natural and idiomatic for describing scenery.