Näkymä oli uskomaton.

• näkymä is a noun meaning view and it is the subject.
• oli is the verb olla (to be) in the past tense, 3rd person singular.
• uskomaton is an adjective meaning incredible / unbelievable. Here it works as a predicate adjective after oli.

So the structure is:

subject + was + adjective

Because oli is the past tense of olla.

• on = is
• oli = was

So if you wanted the present tense, you would say:

Näkymä on uskomaton.

Because this is a very normal Finnish sentence with:

• a singular subject: näkymä
• a predicate adjective describing that subject: uskomaton

Both are in the nominative singular here.

A useful comparison:

• Näkymä oli uskomaton. = singular
• Näkymät olivat uskomattomat. = plural

So yes, the adjective usually agrees with the subject in number in this kind of sentence.

Finnish does not have articles like English a/an and the.

So näkymä can mean:

• a view
• the view

The exact meaning depends on the context.

Yes, literally it is very close to unbelievable.

But in everyday use it often means:

• incredible
• amazing
• fantastic

So it can sound very positive, just like English unbelievable can.

In this sentence, uskomaton is correct because the subject is a singular countable noun: näkymä.

With that kind of subject, the predicate adjective is normally in the nominative:

• Näkymä oli uskomaton.

The form uskomatonta is the partitive, and it is used in other kinds of situations, often with something more abstract or less clearly countable, for example:

• Se oli uskomatonta. = That was unbelievable.

So for näkymä, use uskomaton.

They are similar, but not identical.

• näkymä = view, what you can see from a particular point
• maisema = landscape / scenery, the broader natural or visual scene

So näkymä often focuses more on the sight in front of you, while maisema can sound a bit broader or more scenic.

A rough guide:

• ä sounds somewhat like the vowel in English cat, but shorter and cleaner
• y is like German ü or French u — English does not really have this sound

Also, Finnish stress normally falls on the first syllable:

• NÄ-ky-mä
• O-li
• US-ko-ma-ton

Yes, Finnish word order is more flexible than English, but Näkymä oli uskomaton is the most neutral and natural order.

If you change the order, the meaning usually stays similar, but the emphasis changes. For example:

• Uskomaton oli näkymä.

This sounds more dramatic or literary.

So for a learner, the original order is the safest choice.

-maton / -mätön is a useful Finnish adjective ending. It often gives a meaning like:

• un-
• not able to be -ed
• without having been -ed

So uskomaton is basically:

• not believable
• therefore incredible / unbelievable

Other examples:

• unohtumaton = unforgettable
• syömätön = uneaten

So learning -maton / -mätön is very helpful for vocabulary building.