Wir gehen um den See.

Because um takes the accusative case when it means around in a sentence like this.

• der See = nominative, the form you would use for the subject
• den See = accusative, the form used here because it is the object of the preposition um

So:

• der See = the lake
• um den See = around the lake

This is a very common thing to watch for in German: the preposition often determines the case.

Here, um means around.

So um den See means around the lake.

Be careful, though: um has several meanings in German depending on context, for example:

• um den See = around the lake
• um 8 Uhr = at 8 o’clock
• Es geht um Geld. = It is about money.

So the meaning of um depends a lot on the sentence.

In this sentence, gehen is usually understood as walk.

Literally, gehen often corresponds to go, but when talking about moving on foot, English often prefers walk. So in context:

• Wir gehen um den See. = We are walking around the lake.

German uses gehen in places where English might naturally use walk.

This is the normal German main-clause word order:

• Wir = subject
• gehen = conjugated verb
• um den See = prepositional phrase

So it follows the usual pattern:

subject + verb + other information

German main clauses normally put the conjugated verb in the second position. Since Wir comes first, gehen must come next.

You could also change the order for emphasis:

• Um den See gehen wir.

That is grammatically possible, but less neutral.

Wir is nominative because it is the subject of the sentence.

It is the form meaning we.

A quick comparison:

• wir = we
• uns = us

So:

• Wir gehen ... = We go / We are walking ...
• Er sieht uns. = He sees us.

Because all nouns are capitalized in German.

So:

• wir is not capitalized here because it is a pronoun
• gehen is not capitalized because it is a verb
• See is capitalized because it is a noun

This is one of the most visible spelling differences between German and English.

In this sentence, der See means lake.

This is a famous German vocabulary trap:

• der See = lake
• die See = sea

So the article matters a lot here.

Also note that das Meer is another very common word for sea.

Yes, you often could.

Both can work, but there is a slight difference in feel:

• gehen = go / walk
• laufen = run in some regions, but in many contexts also walk

Because regional usage varies, gehen is the safest and most neutral choice for walking.
If you specifically mean jogging/running around the lake, then laufen may be the better word in many contexts.

So Wir gehen um den See is a very natural, neutral sentence.

Not exactly.

Um den See gehen clearly means to go/walk around the lake.

But umgehen is a different verb, and it can have other meanings such as:

• avoid / bypass
• deal with, in phrases like mit etwas umgehen

So for a beginner, it is best not to treat them as the same thing.

• Wir gehen um den See. = We walk around the lake.
• Wir umgehen das Problem. = We avoid / get around the problem.

German does not form the present continuous the same way English does.

English often says:

• We are walking around the lake.

But German usually just uses the normal present tense:

• Wir gehen um den See.

That sentence can mean:

• We go around the lake
• We are walking around the lake

The exact meaning depends on context. German very often uses the simple present where English would prefer am/is/are + -ing.

Yes. With a normal singular countable noun like See, German usually needs an article in this kind of sentence.

So:

• um den See = around the lake

Leaving out den would sound wrong in standard German here.

German uses articles more regularly than English in many situations, so it is a good habit to learn nouns together with their articles:

• der See
• der Hund
• die Stadt
• das Haus

See is pronounced approximately like zay, but with a long vowel: zeh.

A rough guide for the whole sentence:

• Wir ≈ veer
• gehen ≈ GAY-en
• um ≈ oom
• den ≈ dain
• See ≈ zay

A more German-like pronunciation would be:

veer GAY-en oom dain ZAY

The s in See is pronounced like z in English.