Learn Hardcore Portuguese (Portugal): Eu quero visitar o observatório amanhã à noite. - I want to visit the observatory tomorrow night.

Leaving out eu (Quero visitar o observatório...) sounds very natural and is extremely common in speech.
Including eu (Eu quero...) can add a bit of emphasis on I, like “I want to visit... (not someone else)” or just be neutral, depending on intonation.

So yes, you can absolutely say Quero visitar o observatório amanhã à noite.

Why is it quero visitar and not something like quero visito or quero a visitar?

The verb querer (to want) is followed directly by an infinitive in Portuguese, without a preposition and without conjugating the second verb:

quero visitar = I want to visit
quero comer = I want to eat
quero ir = I want to go

So:

❌ quero visito – wrong, because you’re conjugating visitar instead of using the infinitive.
❌ quero a visitar – wrong in standard Portuguese; you don’t put a preposition here.
✅ quero visitar – correct.

This structure is very similar to English want to + verb, except Portuguese doesn’t need the word to.

How is quero formed? What are the main forms of querer?

Quero is the 1st person singular (I) of querer in the present tense.

Present tense of querer (European Portuguese):

eu quero – I want
tu queres – you want (informal singular)
ele / ela / você quer – he / she / you (formal) want
nós queremos – we want
vocês querem – you (plural) want
eles / elas querem – they want

In everyday speech in Portugal, tu and você usage varies by region and formality, but the verb forms above remain the same.

Why do we say o observatório and not just observatório?

Portuguese uses the definite article (o, a, os, as) much more than English.

o observatório = the observatory
um observatório = an observatory
observatório on its own is possible in some limited contexts (titles, lists, headlines), but in a normal sentence, a singular countable noun usually needs an article.

In Eu quero visitar o observatório, you’re talking about a specific observatory (one that is known in the context), so o (masculine singular) is used.

If it were more general, you could say:

Quero visitar observatórios. – I want to visit observatories. (no article with a plural, more general/indefinite idea)

Could I say ao observatório instead of o observatório here?

Not with visitar.

visitar takes a direct object (no preposition):
- visitar o observatório – to visit the observatory
ir (to go) usually takes a
- article → ao / à:
  - ir ao observatório – to go to the observatory

So:

✅ Quero visitar o observatório. – I want to visit the observatory.
✅ Quero ir ao observatório. – I want to go to the observatory.
❌ Quero visitar ao observatório. – incorrect.

Why is the time expression at the end: amanhã à noite? Can it go at the beginning?

In Portuguese, time expressions are quite flexible in position. All these are correct:

Eu quero visitar o observatório amanhã à noite.
Amanhã à noite, eu quero visitar o observatório.
Amanhã à noite quero visitar o observatório.

Putting amanhã à noite at the end (as in your sentence) is very common and sounds natural. Moving it to the front can add a bit of emphasis on when:

Amanhã à noite quero visitar o observatório.
→ Emphasis: Tomorrow night is when the visit will happen.

What exactly does amanhã à noite mean, and how is à noite different from de noite?

Amanhã à noite literally means tomorrow at night, i.e. tomorrow evening / tomorrow night.

à noite (with grave accent) = in the evening / at night (more like a specific period of the day)
de noite = at night / during the night (more general, often contrasts with de dia – during the day)

Examples:

Costumo estudar à noite. – I usually study in the evenings.
Os gatos veem melhor de noite. – Cats see better at night (at night in general).

In your sentence, amanhã à noite is the standard way to say tomorrow evening / tomorrow night.

Why does à have that accent? What’s the difference between a and à here?

À (with a grave accent) in à noite is a contraction of:

preposition a (to / at)
- definite article a (the, feminine singular)

So:

a (prep.) + a (article) → à

Noite is feminine (a noite = the night), so you get:

à noite = at the night → at night / in the evening

Compare:

Vou à escola. = Vou a + a escola → I’m going to the school.
Vou ao cinema. = Vou a + o cinema → I’m going to the cinema.

Plain a without accent could be:

the preposition a (to, at) not contracted (e.g. dar algo a alguém)
or the feminine indefinite article uma shortened in some expressions (but that’s another topic).

In à noite, the grave accent always signals this contraction a + a.

How do I pronounce amanhã à noite and observatório in European Portuguese?

Approximate European Portuguese pronunciation (not strict IPA, just a guide):

amanhã ≈ uh-muh-NYAH
- ã is a nasal sound, like “an” in French sans.
à (in à noite) ≈ ah (short and open)
noite ≈ NOY-t(uh)
- final e is very reduced, like a quick “uh” or almost silent: NOYT.
observatório ≈ oob-zair-vuh-TÓ-ryoo (EP: final -io often like -ryu)
- Stress on -tó-: ob-ser-va-TÓ-rio.

Putting it together:

Eu quero visitar o observatório amanhã à noite.
≈ Ew KEH-roo vee-zee-TAR oo oob-zair-vuh-TÓ-ryu uh-muh-NYAH ah NOYT(uh).

Note: In European Portuguese, many unstressed vowels (especially final e and o) are very reduced or almost swallowed.

Does Eu quero... sound too direct or rude? Are there more polite ways to say this in Portugal?

Eu quero... is grammatically fine, but in European Portuguese it can sound quite direct in some contexts, especially with requests.

For talking about plans (as in your sentence), it’s perfectly normal:

Eu quero visitar o observatório amanhã à noite. – neutral.

For polite requests (to a stranger, in a shop, etc.), people often prefer softer forms such as:

Gostava de visitar o observatório amanhã à noite. – I would like to visit...
Queria visitar o observatório amanhã à noite. – Literally “I wanted to visit...”, used like I would like to...

These sound more courteous in European Portuguese.

Is quero visitar talking about the future, like I’m going to visit? How is that different from vou visitar?

Yes, in context quero visitar usually refers to a future action, but it focuses on the desire/intention, not the fact that it’s already arranged.

Quero visitar o observatório amanhã à noite.
→ I want to visit (I have the wish/intention to do it tomorrow night).
Vou visitar o observatório amanhã à noite.
→ I’m going to visit (it’s more decided/planned; you’re expressing a future action).

Both can refer to tomorrow night; the nuance is:

quero = what you want to do
vou = what you are going to (intend and plan) to do

There is also a formal future:

Visitarei o observatório amanhã à noite. – grammatically correct but sounds quite formal or literary in everyday European Portuguese.