kouen de kireina hana wo mimasita.

で marks the place where an action happens.

In 公園で きれいな花を 見ました, the action is 見ました (saw), and it happened at the park, so 公園で means in/at the park.

A very common comparison is:

• で = where an action takes place
• に = destination, existence, or specific time in some cases

So:

• 公園で見ました = saw it at the park
• 公園に行きました = went to the park

きれい is a な-adjective, not an い-adjective.

That means when it comes directly before a noun, it takes な:

• きれいな花 = a pretty/beautiful flower
• 静かな町 = a quiet town

By contrast, an い-adjective already ends in い and does not need な:

• 大きい花 = a big flower

Even though きれい ends in い, it is still grammatically a な-adjective. That is something learners just have to memorize.

Yes. な is used when きれい directly modifies a noun.

So:

• きれいな花 = a beautiful flower
  (きれい directly describes 花)

But if きれい is at the end of a sentence or used with です, you do not use な:

• 花はきれいです = The flower is beautiful

So:

• before a noun: きれいな + noun
• as a predicate: きれいです

を marks the direct object of the verb—the thing being acted on.

Here, the verb is 見ました (saw), so the thing that was seen is:

• 花を見ました = saw flowers / saw a flower

So 花 is the direct object, and を shows that clearly.

Also, even though it is written を, it is usually pronounced o in modern Japanese.

Japanese normally places the main verb at the end of the sentence.

So this sentence is structured like:

• 公園で = in the park
• きれいな花を = beautiful flowers
• 見ました = saw

A natural literal order would be:

• In the park, beautiful flowers saw

Of course, in natural English we say:

• I saw beautiful flowers in the park

This verb-final pattern is one of the most important differences between Japanese and English.

Japanese often omits the subject when it is clear from context.

So 公園で きれいな 花を 見ました could mean:

• I saw beautiful flowers in the park
• We saw beautiful flowers in the park
• sometimes even He/She saw beautiful flowers in the park

In many learning materials, it is translated as I saw beautiful flowers in the park, but the sentence itself does not explicitly say I.

This is very normal in Japanese.

見ました is the polite past form of 見る (to see / to look at / to watch, depending on context).

Breakdown:

• dictionary form: 見る
• polite non-past: 見ます
• polite past: 見ました

So 見ました means:

• saw
• sometimes looked at
• sometimes watched

In this sentence, saw is the most natural translation.

It can mean flower or flowers. Japanese nouns usually do not show singular vs. plural unless the context makes it clear.

So きれいな花を見ました could mean:

• I saw a beautiful flower
• I saw beautiful flowers

If the provided meaning says flowers, that is a natural interpretation, but the Japanese itself is flexible.

The same is true for articles:

• no built-in a
• no built-in the

Context decides.

Because this sentence is focused on the action itself, and the topic may already be understood from context.

A version with は is also possible, for example:

• 私は公園できれいな花を見ました。
  = I saw beautiful flowers in the park.

Here, 私は sets I as the topic.

But Japanese often leaves that out when it is obvious, so the shorter sentence sounds natural.

No. In normal Japanese writing, spaces are usually not used between words.

So this would normally be written as:

• 公園できれいな花を見ました。

Learning materials often add spaces to help beginners see the parts more easily:

• 公園 / で / きれいな / 花 / を / 見ました

That is useful for study, but not standard everyday writing.

No, that would sound wrong here.

Use で because the park is the place where the seeing happened:

• 公園で花を見ました = correct

Using に with 見る in this sentence does not mark the location of the action properly.

However, に would be correct with other verbs, such as:

• 公園に行きました = went to the park
• 公園に花があります = there are flowers in the park

So the choice depends on the role of the location in the sentence.

Yes. The full noun phrase is:

• きれいな花

This means beautiful flower(s).

Then を marks that whole phrase as the direct object:

• きれいな花を

So you can think of it as:

• [beautiful flowers] + object marker

The adjective and noun stay together as one unit, and を attaches to that unit.