A kilátóig nagy a szintkülönbség.

Kilátóig is kilátó + -ig.

• kilátó = lookout tower / viewpoint
• -ig = up to, as far as, until

So a kilátóig means up to the lookout or as far as the lookout.

This ending is very common with both places and times:

• a hídig = up to the bridge
• Budapestig = as far as Budapest
• öt óráig = until five o’clock

In this sentence, it marks the endpoint of the route.

Because Hungarian normally keeps the definite article before a noun even when that noun has a case ending.

So you get:

• a kilátó = the lookout
• a kilátóig = up to the lookout
• a kilátónál = at the lookout
• a kilátóhoz = to the lookout

English often drops the article in similar expressions, but Hungarian usually does not. Here, the speaker is referring to a specific lookout.

Szintkülönbség is a compound word:

• szint = level
• különbség = difference

So literally it means difference in level.

In hiking or route descriptions, it usually refers to the vertical difference in height between two points, so in natural English it can often be expressed as:

• elevation difference
• elevation gain
• a big climb

Depending on context, this sentence could sound natural in English as There’s a big elevation gain up to the lookout or It’s a steep climb to the lookout.

Because in Hungarian, the present tense of to be is usually omitted in the 3rd person singular and plural when the predicate is a noun or adjective.

So:

• A ház nagy. = The house is big.
• A szoba tiszta. = The room is clean.
• Nagy a szintkülönbség. = The elevation difference is big.

So nagy a szintkülönbség is completely normal Hungarian.

If you use a different structure, you may get van, for example:

• Nagy szintkülönbség van a kilátóig. = There is a big elevation difference up to the lookout.

Both are correct, but they are built differently.

Hungarian word order is flexible, and it often reflects focus or what is being presented as the important information.

Nagy a szintkülönbség is a very natural pattern in Hungarian. It puts the emphasis on the quality nagy first: the important point is that the elevation difference is large.

Compare:

• Nagy a szintkülönbség. = The elevation difference is large.
  
  • natural, common
• A szintkülönbség nagy. = The elevation difference is large.
  
  • also grammatical, but often feels more neutral, explanatory, or contrastive

So the version in your sentence is not strange at all; it is a very normal Hungarian way to phrase it.

In this sentence, the speaker is talking about the specific elevation difference on that route, so Hungarian uses the definite article: a szintkülönbség.

Hungarian often uses the definite article with abstract nouns when the thing is identifiable from context.

Compare these two structures:

• Nagy a szintkülönbség. = The elevation difference is big.
• Nagy szintkülönbség van a kilátóig. = There is a big elevation difference up to the lookout.

The first treats it as a known, specific thing.
The second introduces it more like there is a big amount of elevation difference.

Both are possible, but they are slightly different in structure and feel.

Starting with A kilátóig sets the frame first: as far as the lookout / up to the lookout.

This is very common in Hungarian. The speaker first establishes the route or limit, then says something about it:

• A kilátóig nagy a szintkülönbség.
• A faluig messze van.
• A hídig jó az út.

It is a bit like saying: As far as the lookout is concerned, the elevation difference is large.

A more neutral variant would also be:

• Nagy a szintkülönbség a kilátóig.

That means essentially the same thing.

Not with exactly the same meaning.

• -ig = up to / as far as
• -hoz/-hez/-höz = to / toward

So:

• a kilátóig = up to the lookout, as far as the lookout
• a kilátóhoz = to the lookout

In this sentence, -ig is more natural because the speaker is talking about the extent of the route and the elevation difference measured up to that endpoint.

If you say a kilátóhoz, it sounds more like simple direction toward the lookout, not so much the endpoint of a measured stretch.

It can be understood both ways depending on context.

Literally, it is closer to:

• The elevation difference up to the lookout is large.

But in natural English, especially in a hiking context, people often say:

• It’s a steep climb to the lookout.
• There’s a lot of elevation gain to the lookout.

So the Hungarian sentence is somewhat more technical on the surface, but in real use it may simply mean that getting to the lookout involves a lot of uphill climbing.