Learn Hardcore Indonesian: Di antara dua gunung tinggi itu ada sebuah lembah hijau yang sering dikunjungi pelancong. - Between those two tall mountains there is a green valley that tourists often visit.

Di antara literally means “in between / among” and introduces a location: “Di antara dua gunung tinggi itu…” = “Between those two tall mountains…”.

di = at / in / on (location preposition)
antara = between / among

You can move this phrase to the end without changing the meaning much:

Ada sebuah lembah hijau di antara dua gunung tinggi itu.
“There is a green valley between those two tall mountains.”

Spelling note: as a preposition, the correct spelling is di antara (two words), not diantara in standard Indonesian.

Why is itu placed after dua gunung tinggi instead of before the noun, like in English “those two tall mountains”?

In Indonesian, demonstratives like ini (this/these) and itu (that/those) usually come after the whole noun phrase they modify:

dua gunung tinggi itu
= “those two tall mountains” (literally: “two mountains tall that”)

Structure:
[dua] [gunung] [tinggi] [itu]
[number] [noun] [adjective] [demonstrative]

You generally do not say itu dua gunung tinggi when you simply mean “those two tall mountains”; that order either sounds odd or would need extra context (more like “those are two tall mountains”).

So: put itu at the end of the noun phrase it refers to.

What is the role of ada in this sentence? Is it like “is/are” or “there is/are”, and is it necessary?

Here, ada is an existential verb meaning “there is / there are”:

Ada sebuah lembah hijau…
= “There is a green valley…”

It does not mean “to be” in the same way as English is/are linking a subject to an adjective (for that, Indonesian often omits a verb: Gunung itu tinggi = “That mountain is tall”).

In this sentence, ada is natural and standard.
Without ada:

Di antara dua gunung tinggi itu sebuah lembah hijau…

sounds incomplete or poetic at best. In normal prose, keep ada to clearly express existence: “there is/are”.

Why do we have sebuah before lembah? Can it be omitted?

Sebuah is a classifier/article that often corresponds to “a / one (piece of)” for many countable, inanimate nouns:

sebuah lembah hijau
= “a green valley” / “one green valley”

You can omit it:

Ada lembah hijau…
still means “There is a green valley…”, just a bit more neutral and less specific about “one”.

Nuance:

ada sebuah lembah hijau → slightly more “one particular valley”.
ada lembah hijau → “there is a green valley” in a more general sense.

Both are grammatically correct; sebuah adds a bit of “one specific unit” feeling.

Why is it lembah hijau and gunung tinggi, not hijau lembah or tinggi gunung? Are adjectives always after nouns?

In noun phrases, descriptive adjectives normally come after the noun:

gunung tinggi = tall mountain
lembah hijau = green valley
rumah besar = big house
mobil merah = red car

So the pattern is generally:

noun + adjective

If you say hijau lembah or tinggi gunung, it doesn’t mean “green valley / tall mountain” as a normal noun phrase; it instead sounds like:

hijau lembah itu ~ “the greenness of the valley” (poetic / special structure)
tinggi gunung itu ~ “the height of the mountain”

For basic descriptions, keep adjectives after nouns.

How does the part yang sering dikunjungi pelancong work? What does yang do?

Yang introduces a relative clause, similar to “that / which / who” in English.

lembah hijau yang sering dikunjungi pelancong
= “the green valley that is often visited by travelers”

Breakdown:

lembah hijau = green valley
yang = that / which (relative pronoun)
sering dikunjungi pelancong = is often visited by travelers

So yang … attaches extra information to lembah hijau.
You can think of it as:

[green valley] [which is often visited by travelers]

Why is dikunjungi used instead of mengunjungi? What’s the difference?

This is a passive construction.

mengunjungi = to visit (active)
- Pelancong mengunjungi lembah itu.
  “The travelers visit that valley.”
dikunjungi = to be visited (passive)
- Lembah itu sering dikunjungi pelancong.
  “That valley is often visited by travelers.”

In our sentence, the focus is on the valley, not the travelers, so Indonesian naturally uses the passive:

lembah hijau yang sering dikunjungi pelancong
“the green valley that is often visited by travelers”

If you used mengunjungi here (yang sering mengunjungi pelancong), it would mean:

“which often visits travelers” – making the valley the subject doing the visiting, which is wrong.

In dikunjungi pelancong, why is there no oleh before pelancong? When is oleh needed?

In passive sentences, the agent (the doer) can appear:

with oleh (“by”), or
directly after the verb with no preposition.

Both are possible:

Lembah itu sering dikunjungi pelancong.
Lembah itu sering dikunjungi oleh pelancong.
= “That valley is often visited by travelers.”

Differences:

Without oleh (dikunjungi pelancong) is very common in speech and neutral writing, especially when the agent is short and clear.
With oleh can sound slightly more formal or explicit, and is often used if:
- the agent is long/complex, or
- you really want to emphasize who is doing the action.

Here, oleh is optional; both forms are correct.

Does pelancong mean “tourist(s)” or “traveler(s)”? Is it singular or plural? How is it different from turis or wisatawan?

Pelancong generally means “tourist / traveler”, often with a leisure or sightseeing nuance.

Indonesian usually does not mark singular vs plural on the noun itself:

pelancong can mean “a traveler” or “travelers”, depending on context.
To emphasize plural, you might see para pelancong (“the travelers”).

Comparison:

pelancong – a bit literary/formal; “sightseer / tourist / traveler”.
turis – from “tourist”; very common in everyday speech.
wisatawan – more formal/official; used in media, tourism industry, stats.

In this sentence, pelancong ≈ “tourists / travelers” in a general sense.

Where can sering go? Could we move it somewhere else in the clause?

Sering means “often” and usually appears before the verb or verb phrase:

sering dikunjungi pelancong
“often visited by travelers”

Other natural positions:

Lembah itu sering dikunjungi pelancong.
Pelancong sering mengunjungi lembah itu.

What you normally don’t do:

dikunjungi sering pelancong – unnatural
splitting it far away from the verb in a simple clause

So keep sering directly before the verb (dikunjungi, mengunjungi, etc.) to sound natural.

Could we say lembah yang hijau instead of lembah hijau? Is there a difference in nuance?

Both are possible, but the nuance changes.

lembah hijau
= “a green valley” (simple description, like a basic adjective)
lembah yang hijau
literally “the valley that is green” – often more emphatic or contrastive, for example when contrasting it with other valleys:
- Bukan lembah yang kering, tapi lembah yang hijau.
  “Not the dry valley, but the one that is green.”

In your sentence, sebuah lembah hijau is the most natural, neutral choice.
sebuah lembah yang hijau would sound a bit heavier or more “explaining” than necessary.

Is the overall word order fixed? Could we say Ada sebuah lembah hijau di antara dua gunung tinggi itu instead? Any difference?

You can absolutely say:

Ada sebuah lembah hijau di antara dua gunung tinggi itu.

This is very natural and maybe even more common word order in everyday use:

Di antara dua gunung tinggi itu ada sebuah lembah hijau…
→ Starts with the location between the two mountains, then states what is there.
Ada sebuah lembah hijau di antara dua gunung tinggi itu.
→ Starts with “There is a green valley”, then adds where it is.

Both are correct.
Choice depends on what you want to highlight first:

the place (option 1), or
the existence of the valley (option 2).