chulbaljieneun keun ijeongpyoga hana isseo.

에는 is 에 + 는.

• 에 marks a location: at / in / on
• 는 adds a topic or contrast nuance

So 출발지에는 means something like:

• as for at the starting point
• at the starting point, at least
• there is, at the starting point, ...

In many sentences like this, 는 gives a slight contrast, often implying something like:

• At the starting point, there is a big signpost
  (maybe at another place, there is not)

If you said 출발지에 큰 이정표가 하나 있어, that would still be natural, but it would sound more neutral and less contrastive.

출발지 means starting point, place of departure, or departure location.

It is made up of:

• 출발 = departure / setting off
• 지 = place, location

So literally, it is the place you leave from.

Depending on context, it could mean:

• the start of a hiking trail
• the departure point on a map
• the place where a trip begins

크다 is the dictionary form meaning to be big.

When a descriptive verb (often called an adjective in English-based Korean learning) comes directly before a noun, it changes form.

So:

• 크다 = to be big
• 큰 = big, when modifying a noun

That is why:

• 큰 이정표 = a big signpost

This is similar to:

• 작다 → 작은 = small
• 예쁘다 → 예쁜 = pretty

So 큰 is just the noun-modifying form of 크다.

Literally, it is close to:

• there exists one signpost
• there is one signpost

Breaking it down:

• 이정표가 = signpost + subject marker
• 하나 = one
• 있어 = exists / there is

So the sentence structure is an existence sentence, very common in Korean:

• [place]에/에는 [thing]이/가 있어요
• There is [thing] at [place].

Here, the thing is:

• 큰 이정표가 하나 = one big signpost

In Korean, numbers often come after the noun, especially when counting things.

So Korean commonly says:

• 이정표가 하나 = one signpost
• literally, signpost one

This is normal Korean word order.

You will often see:

• 사람이 두 명 있어요 = There are two people.
• 책이 세 권 있어요 = There are three books.

Sometimes a counter is required. With 하나, everyday speech often leaves the counter out when it is obvious. So 이정표가 하나 있어 is completely natural.

가 marks 이정표 as the thing that exists.

In existence sentences with 있다, Korean often uses 이/가 for the thing being present:

• 책이 있어요 = There is a book.
• 고양이가 있어요 = There is a cat.

So:

• 이정표가 하나 있어 = There is one signpost.

If you used 이정표는, the nuance would change. It might sound like:

• As for the signpost, there is one or it could set up a contrast.

In this sentence, 가 is the most natural choice because the speaker is simply identifying what is there.

이정표 usually means a signpost, guide sign, or direction marker.

It often suggests something that helps show:

• directions
• routes
• destinations
• distances

표지판 is a broader word for a sign or signboard.

So:

• 이정표 = more specifically a directional sign / waymarker
• 표지판 = a general sign

In some contexts, both could be translated as sign, but 이정표 has a more specific direction-guiding feeling.

있어 is the casual/informal polite-low style.

Compare:

• 있어 = casual
• 있어요 = polite
• 있다 = dictionary/plain form

So the sentence could appear as:

• 출발지에는 큰 이정표가 하나 있어.
  casual, used with friends, in narration, or relaxed explanation
• 출발지에는 큰 이정표가 하나 있어요.
  polite, more suitable for everyday conversation with strangers or learners
• 출발지에는 큰 이정표가 하나 있다.
  plain/written style, common in writing or neutral statements

The meaning is basically the same; the speech style changes.

Normally, 하나 있어 is understood as there is one.

In many contexts, that strongly suggests exactly one. For example, if someone is describing what is at the departure point, the listener will usually understand:

• There is one big signpost there.

However, real-life interpretation depends on context. Sometimes speakers are not being mathematically precise and just mean:

• there's a big signpost there with 하나 adding a natural counting flavor.

Still, the default reading is one.

Yes. In natural English, there is a big signpost is often the best translation.

Korean frequently includes 하나 in places where English does not have to say one. So:

• 큰 이정표가 하나 있어
  can be translated naturally as
• There is a big signpost.

If you want to emphasize the number, then:

• There is one big signpost.

Both are possible; the best choice depends on how important the number is in context.

A very useful pattern is:

• [place]에/에는 [noun]이/가 [number] 있어요
• There is/are [number] [noun](s) at [place].

Using this sentence as a model:

• 출발지에는 큰 이정표가 하나 있어.

Similar examples:

• 교실에는 학생이 세 명 있어요.
  There are three students in the classroom.
• 책상 위에는 책이 두 권 있어요.
  There are two books on the desk.
• 공원에는 큰 나무가 많아요.
  There are many big trees in the park.

So this sentence is great for learning:

1. location marking with 에/에는
2. noun-modifying adjectives like 큰
3. existence with 있다
4. counting after nouns in Korean