Learn Hardcore Polish: Lubię marzyć o podróżach, kiedy siedzę w pracy przy biurku. - I like to dream about travels when I sit at my desk at work.

Lubię marzenia o podróżach. – I like dreams about travels.
→ This means you like those dreams themselves as objects (e.g. in books, in your head), not the activity of daydreaming.

Also, Lubię marzenie o podróżach is not natural, because marzenie is “a (single) dream” as a noun; you’d almost always use the plural marzenia in this kind of sentence.

So Lubię marzyć = I enjoy the activity of dreaming, which is exactly what’s meant here.

What case is podróżach in o podróżach, and why do we need that form?

Podróżach is in the locative plural.

The preposition o (“about”) in the sense “about, concerning” always takes the locative case:

myśleć o czymś – to think about something
mówić o czymś – to talk about something
marzyć o czymś – to dream about something

The noun podróż (a trip, journey) has:

nominative singular: podróż
locative singular: podróży
nominative plural: podróże
locative plural: podróżach

So after o, if you want the plural, you must say o podróżach.

Why is it plural o podróżach (“about travels”) and not singular o podróży (“about a travel”)?

Both are grammatically correct, but the nuance is different:

o podróżach – about travels / about (going on) trips in general
→ This is generic, like English “about travelling, about trips”. That fits a general hobby: you like daydreaming about going places.
o podróży – about the trip / about a trip
→ Singular suggests one specific journey. You’d use it when you have a particular trip in mind:
Marzę o tej podróży. – I dream about this trip.

In the sentence given, we’re talking about a general habit (daydreaming about travelling), so the plural o podróżach is more natural.

Is marzyć o always used with the locative case, and does it always mean “to dream about”?

Yes, marzyć o + locative is the standard pattern, and it always has the general meaning “to dream about / to long for / to daydream about”:

Marzę o wakacjach. – I dream about holidays.
Marzymy o własnym domu. – We dream about (long for) our own house.

It’s usually conscious dreaming or wishing (daydreams, hopes), not necessarily sleep-dreams. For literal sleep dreams you can use śnić o + locative:

Śniłem o podróżach. – I dreamed (in my sleep) about travels.

But grammatically, both marzyć o and śnić o always take the locative.

Why do we use kiedy here? Could we also say gdy or jak instead?

All three are possible, but with slightly different flavors:

kiedy – neutral, very common for “when” in time clauses.
Lubię marzyć…, kiedy siedzę… – perfectly standard.
gdy – more formal/literary, but still common in speech.
Lubię marzyć…, gdy siedzę w pracy przy biurku. – also correct, a bit more “bookish”.
jak – colloquial in this sense; often used in everyday speech:
Lubię marzyć o podróżach, jak siedzę w pracy przy biurku. – would sound informal/regional in many accents.

For a textbook-style sentence, kiedy is the safest choice.

The English translation uses “when I’m sitting”, but Polish has just kiedy siedzę. How do Polish speakers express the idea of “I’m sitting” versus “I sit”?

Polish does not have a separate present continuous form like English. The single present tense siedzę can mean:

I sit (habitually)
I’m sitting (right now)

Context tells you which one is meant.

In our sentence:

kiedy siedzę w pracy przy biurku

can mean both:

when I sit at my desk at work (general habit)
when I’m sitting at my desk at work (each time I happen to be sitting there)

Because the whole sentence describes a general habit (what you like to do in that situation), English naturally chooses “when I’m sitting…”, but Polish doesn’t need a special form for that.

Why is it w pracy for “at work”? Isn’t w usually “in”?

Literally, w means “in, inside”, and it takes the locative case:

w pracy – in/at work (locative of praca)
w domu – at home / in the house
w szkole – at school / in the school

In Polish, w + locative is often used where English can say either “in” or “at”. With certain places connected to activities (work, school, home), w naturally corresponds to English “at”:

Jestem w pracy. – I’m at work.
Dzieci są w szkole. – The children are at school.

Contrast with do pracy – to work (direction, “towards”), which takes the genitive after do.

What is the difference between przy biurku, na biurku, and za biurkiem?

All three are about location relative to the desk, but they’re used differently:

przy biurku (locative of biurko)
- literally: by / at the desk
- typical for a person sitting or working at the desk
- Siedzę przy biurku. – I’m sitting at my desk.
  → This is exactly what we want in the sentence.
na biurku
- literally: on the desk
- used mainly for objects lying on top of the desk:
  Klucze leżą na biurku. – The keys are on the desk.
- For people it would mean physically on top of the desk (unusual, maybe joking or literal).
za biurkiem
- literally: behind the desk
- emphasizes being on the other side of the desk, often with a role/status nuance:
  Dyrektor siedzi za biurkiem. – The director is sitting behind the desk.
- Can imply an “official” position (teacher, boss, clerk).

So in w pracy przy biurku, przy biurku is the natural choice for a person sitting and working.

Could we change the word order to Kiedy siedzę w pracy przy biurku, lubię marzyć o podróżach? Would that change the meaning?

Yes, that word order is perfectly correct, and the meaning stays the same.

Polish word order is quite flexible, especially with clauses. You can have:

Lubię marzyć o podróżach, kiedy siedzę w pracy przy biurku.
Kiedy siedzę w pracy przy biurku, lubię marzyć o podróżach.

The difference is only in emphasis:

Starting with Lubię marzyć… puts slight focus on what you like.
Starting with Kiedy siedzę… puts slight focus on the situation/time.

In both cases you must keep the comma between the main clause and the kiedy clause.

Why don’t we say Ja lubię marzyć…? When do Polish speakers include the pronoun ja?

Polish is a “pro-drop” language: you usually omit subject pronouns because the verb ending already shows the person:

Lubię – I like
Lubisz – you (sg) like
Lubi – he/she/it likes

Poles add ja mainly for:

Emphasis or contrast:
- Ja lubię marzyć, ale on tego nie znosi. – I like to dream, but he hates it.
Clarity, when needed in a complex context.

In a simple, neutral sentence like this, Lubię marzyć… without ja is the natural choice.

What aspect does marzyć have? Could we use pomarzyć here, and how would the meaning change?

Marzyć is imperfective – it describes an ongoing, repeated, or general activity:

Lubię marzyć o podróżach. – I like (generally) to dream about travels.

Pomarzyć is the perfective counterpart and often implies:

dreaming for a while,
a single occasion of dreaming.

Examples:

Chciałbym tylko trochę pomarzyć. – I’d just like to dream a bit.
Usiadłem i pomarzyłem o wakacjach. – I sat down and had a little daydream about holidays.

In your sentence:

Lubię marzyć o podróżach… – neutral, general habit.
Lubię sobie pomarzyć o podróżach… – colloquial, I like to have a little daydream about travels (from time to time).

Both are possible, but the given sentence with marzyć is the standard, neutral version.

Is there any subtle nuance in saying w pracy przy biurku instead of przy biurku w pracy?

Both are grammatically correct and would be understood the same way.

However, the usual, more natural order in Polish is:

bigger / more general place → more specific location

So:

w pracy przy biurku – at work, at (my) desk
(general: at work; then: where exactly at work? at the desk.)

Saying przy biurku w pracy is possible, but it sounds slightly less typical and may put a tiny bit more focus on the desk. In everyday speech, w pracy przy biurku is what people would normally say.