Learn Hardcore Chinese: wǒmen cānguānwán bówùguǎn yǐhòu qù gōngyuán sànbù. - After we finished visiting the museum, we went for a walk in the park.

我们参观博物馆以后去公园散步。
= After we visit the museum, we go to the park for a walk.
(neutral about whether the visit is thoroughly completed; in practice it usually is, but it’s not highlighted.)
我们参观完博物馆以后去公园散步。
= After we finish visiting the museum, we go to the park for a walk.
(highlights the completion of the visit, “once we’re done with the museum…”)

Both are grammatically correct; 完 just adds that sense of “done / finished.”

Why is 以后 in the middle of the sentence? Can it go at the beginning or somewhere else?

In this sentence, 以后 introduces a time clause:

我们参观完博物馆以后 = after we finish visiting the museum

This whole chunk acts like a time expression for the main action:

(After we finish visiting the museum) we go to the park for a walk.

You can move the 以后-clause to the beginning:

参观完博物馆以后，我们去公园散步。
我们参观完博物馆以后，去公园散步。

Putting it at the end like English “We go for a walk in the park after visiting the museum” is less natural if you keep exactly the same structure. You’d more likely say:

我们去公园散步，是在参观完博物馆以后。

So the most natural positions are:

At the start:
参观完博物馆以后，我们去公园散步。
Right before the main action (as in your sentence):
我们参观完博物馆以后去公园散步。

There’s no 了 in this sentence, even though the actions are completed. Is that okay? When would I use 了?

It’s perfectly fine without 了. Chinese doesn’t need a past tense marker in every past sentence. Completion is already expressed by:

参观完 (with 完, “finish visiting”)
Context (for example, a time word like 昨天 “yesterday” if you add it)

If you want to make the completion even more explicit, you can add 了:

我们参观完了博物馆以后去公园散步。
我们参观完博物馆以后去公园散步了。

Both are grammatically okay, but:

参观完了 emphasizes that the visiting itself is completed.
Sentence-final 了 (…散步了) tends to emphasize a change of state or that the whole event is now a done thing.

In everyday speech, the version without any 了 is very natural, especially if context already makes the time clear.

What’s the difference between 以后 and 然后 here? Could I say 参观完博物馆然后去公园散步?

以后 and 然后 are not the same:

以后 = “after”, marking a time relationship (A happens, and then at a later time B happens).
然后 = “then / and then / after that”, marking a sequence of actions in a narrative.

Your sentence uses 以后 to form a time clause:

参观完博物馆以后去公园散步。
= After finishing visiting the museum, (we) go to the park for a walk.

You can say:

我们参观完博物馆，然后去公园散步。

This is more like listing steps:

We visit the museum and finish.
Then we go to the park for a walk.

So:

以后 version feels more like “once we’re done with the museum, we go for a walk (after that point in time).”
然后 version feels like narrating a sequence: “first this, then that.”

Why is it 去公园散步 and not 去散步在公园 like in English “go walk in the park”?

Chinese word order is different here. The typical pattern is:

去 + place + action

So:

去公园散步
= go to the park (and) walk / go for a walk in the park

Saying 去散步在公园 is unnatural because:

去 normally takes a place right after it (where you go).
在公园散步 is fine by itself (“take a walk in the park”), but when you add 去, you usually put the place after 去:

Correct patterns:

去公园散步
在公园散步
去公园，在那儿散步。

Unnatural:

去散步在公园 ✗

What’s the nuance of 散步 compared with 走路 or 步行?

散步 = to take a walk / go for a stroll, usually leisurely and for relaxation or light exercise.
- 去公园散步 = go to the park for a (leisure) walk.
走路 = to walk (as a way of moving), often contrasted with driving, taking the bus, etc.
- 我走路去学校。 = I walk to school (not by car, bus, etc.).
  You can say 在公园走路, but it doesn’t automatically sound as leisurely as 散步.
步行 = walk on foot, more formal or written, often in notices or official language.
- 请步行通过。 = Please pass through on foot.

In a sentence about relaxing in a park, 散步 is the most natural choice.

In 参观完博物馆, is 博物馆 the object of 参观 or of 完? How does this grammar work?

博物馆 is the object of the verb 参观.

Structure:

参观 (verb: to visit, to tour)
完 (resultative complement: to finish)
博物馆 (object: the museum)

So the underlying pattern is:

Verb + Resultative Complement + Object

Here: 参观 + 完 + 博物馆

You can think of it as:

“(We) visit-finish the museum.”

The complement 完 attaches to the verb, not to the object. It tells you the result of the action (the visit is finished).

Can I say 参观了博物馆以后 instead of 参观完博物馆以后? What’s the difference?

Yes, you can say:

我们参观了博物馆以后去公园散步。

Differences in nuance:

参观了博物馆以后…
Uses 了 to indicate that the action happened / is completed. It’s a more general “did it” feeling.
参观完博物馆以后…
Uses 完 to emphasize finishing the action, like “once we’re done visiting the museum…”

In many contexts, they can both describe the same real-world situation. 完 just puts a bit more focus on the completion of the visit, while 了 is a broader past/completed aspect marker.

Can we omit 我们 in this sentence? When would that be natural?

Yes, you can omit 我们 if it’s clear from context who the subject is:

参观完博物馆以后去公园散步。

This is common in Chinese because subjects are often dropped when:

They’re obvious from previous sentences (you’ve already said you’re talking about “we”).
It’s a plan or instruction involving “us” or “everyone,” like on an itinerary or in a group setting.

For example, on a schedule you might just see:

上午参观博物馆，参观完博物馆以后去公园散步。

In a self-contained single sentence with no context, including 我们 makes it clearer to a learner, but native speakers often omit it when it’s already known.

How can I make this sentence clearly about the future vs clearly about the past?

Chinese doesn’t change the verb form for tense. You use time words and sometimes aspect markers.

1. Clearly future

Add future time expressions or future markers:

明天我们参观完博物馆以后去公园散步。
Tomorrow, after we finish visiting the museum, we’ll go for a walk in the park.
等我们参观完博物馆以后，就去公园散步。
When we finish visiting the museum, then we’ll go for a walk in the park.
(The 就 here helps show a planned sequence.)

2. Clearly past

Add past time expressions or sometimes sentence-final 了:

昨天我们参观完博物馆以后去公园散步了。
Yesterday, after we finished visiting the museum, we went for a walk in the park.
上个星期天，我们参观完博物馆以后又去公园散步。
Last Sunday, after we finished visiting the museum, we also went for a walk in the park.

The basic structure of the sentence stays the same; you just anchor it in time with context words like 昨天, 明天, 刚才, 以后 in a more general sense, etc.

Why is there no comma in 我们参观完博物馆以后去公园散步? Could I write a comma there?

In everyday writing, people often write:

我们参观完博物馆以后，去公园散步。

The comma makes the structure visually clearer:

[我们参观完博物馆以后]， [去公园散步]

Without the comma, it’s still grammatically correct, especially in shorter, simple sentences like this. In more formal or careful writing, using the comma after the 以后-clause is common and recommended:

参观完博物馆以后，我们去公园散步。

So:

With comma: more clear and standard, especially in print.
Without comma: still acceptable, seen often in casual writing or teaching materials.

Could I say 以后我们参观完博物馆去公园散步? Is that natural?

以后我们参观完博物馆去公园散步 is grammatically understandable, but it’s awkward and can be confusing, because 以后 usually directly connects to what comes right after it as a time phrase.

More natural patterns are:

以后，我们参观完博物馆就去公园散步。
In the future, after we finish visiting the museum, we’ll go for a walk in the park.

or keep 以后 inside the clause it belongs to:

我们参观完博物馆以后去公园散步。
参观完博物馆以后，我们去公园散步。

If you want to start with 以后 to mean “from now on / in the future, whenever this happens…”, you need a clearer structure, for example:

以后，每次参观完博物馆，我们都去公园散步。
In the future / From now on, every time we finish visiting the museum, we’ll go to the park for a walk.

So it’s better not to say 以后我们参观完博物馆去公园散步 in isolation; revise it slightly to one of the more natural versions above.