Post la kaverno ni vidis belan panoramon.

Because panoramon is the direct object of vidis.

In Esperanto, the thing directly affected by the verb usually takes the accusative ending -n. So:

• Ni vidis panoramon = we saw a panorama

Here, we are doing the seeing, and the panorama is what was seen, so panoramo becomes panoramon.

Because adjectives in Esperanto agree with the nouns they describe.

Since panoramon is:

• singular
• accusative

the adjective describing it must match:

• bela panoramo = a beautiful panorama
• belan panoramon = a beautiful panorama (as a direct object)

This agreement happens for both number and case:

• bela panoramo
• belaj panoramoj
• belan panoramon
• belajn panoramojn

Because kaverno is the object of the preposition post, not the direct object of the verb.

Normally, Esperanto prepositions take a noun without -n:

• en la domo
• sub la tablo
• post la kaverno

So here, post la kaverno is just a prepositional phrase meaning something like after the cave.

The direct object is still belan panoramon, not kaverno.

Yes. Post usually means after.

It can be used:

• in time: post la tagmanĝo = after lunch
• in sequence or position along a route: post la kaverno = after the cave

But note that post does not usually mean physical behind in the sense of location at the back of something. For that, Esperanto normally uses malantaŭ.

So:

• post la kaverno = after the cave
• malantaŭ la kaverno = behind the cave

Because Esperanto word order is flexible, and putting Post la kaverno first helps set the scene.

This sentence could also be written as:

• Ni vidis belan panoramon post la kaverno.

That would still be correct.

Starting with Post la kaverno gives a natural context first feel: first the location/point in the route, then what happened there.

Because Esperanto marks the direct object with -n, word order does not have to do as much grammatical work as it does in English.

Because Esperanto has a definite article, la, but no indefinite article.

So:

• la kaverno = the cave
• panoramo can mean a panorama or just panorama, depending on context

In this sentence, la kaverno refers to a specific cave already known or identifiable in context, while belan panoramon does not need an article.

English forces you to choose between a and the. Esperanto only marks definiteness when needed with la.

Vidis is the past tense form of the verb vidi = to see.

It breaks down like this:

• vid- = the root meaning see
• -is = past tense

So:

• vidas = see / am seeing
• vidis = saw
• vidos = will see

Esperanto tense endings are very regular, so once you know them, verbs become much easier to recognize.

By itself, post la kaverno simply means after the cave. The exact nuance comes from context.

It could mean:

• after passing the cave on a route
• after the cave as a landmark
• after the cave section of a journey

If you specifically wanted to say after coming out of the cave, Esperanto would usually say that more explicitly, for example:

• post eliro el la kaverno
• post kiam ni eliris el la kaverno

So the original sentence is a bit broader and less specific.

Yes. Esperanto allows both positions:

• belan panoramon
• panoramon belan

But belan panoramon is the more normal, neutral order.

Putting the adjective after the noun can sound more literary, emphatic, or stylistically marked. For most everyday sentences, learners should usually put the adjective before the noun unless they have a special reason not to.