Learn Hardcore Russian: По выходным я езжу в центр до станции метро «Парк», а потом иду пешком. - On weekends I go to the center to the metro station “Park,” and then I walk.

По выходным literally means “by the weekends / along the weekends”, but idiomatically it means “on weekends” in the sense of regularly, every weekend.

по + dative plural (по выходным) often expresses repeated / habitual time:
- по вечерам – in the evenings (regularly)
- по понедельникам – on Mondays (as a rule)

So По выходным я езжу… = I (usually) go on weekends…, not just once.

Why is выходным in the dative plural after по?

In this meaning of “on (each) [day/time]”, the preposition по requires the dative plural:

по выходным – on weekends
по субботам – on Saturdays
по утрам – in the mornings

So выходные (weekends/days off, nominative plural) becomes выходным in the dative plural after по in this habitual-time construction.

Could I say На выходных or В выходные instead of По выходным? What’s the difference?

All three exist, but they’re not identical in feel:

По выходным – on weekends regularly, as a habit.
На выходных – (this/that) weekend, or on weekends in a more general, less “every time” way.
- На выходных я поеду к друзьям. – This coming weekend I’ll go to my friends.
В выходные – also on the weekend(s), but less common; often used similarly to на выходных in conversational speech.

In your sentence, По выходным is perfect because the action is habitual.

Why is it я езжу and not я еду?

Russian motion verbs distinguish one-time / right-now movement vs habitual / repeated movement:

ехать (я еду) – to go by transport right now / one specific trip
ездить (я езжу) – to go by transport regularly, back and forth

Since the sentence describes what you do on weekends in general (a repeated action), you use ездить – я езжу.

If you were talking about what you are doing today, this particular time, you’d say:

Сегодня я еду в центр до станции метро «Парк». – Today I’m going to the center to Park metro station.

Why is it езжу and later иду, not the same verb each time?

Russian uses different motion verbs depending on how you move:

ездить / ехать – by transport (car, bus, metro, etc.)
ходить / идти – on foot

So the structure is:

я езжу в центр до станции метро… – I go (by vehicle) to the center, up to the metro station…
а потом иду пешком – and then (I) go on foot.

It would be odd to mix these: идти is not used for going by metro/bus, and ехать is not used for walking.

What’s the difference between ездить and ходить, since both can mean “to go” repeatedly?

Both are repeated / habitual motion verbs, but with different means of transport:

ездить – to go by some vehicle repeatedly:
- Я езжу в центр на автобусе. – I go to the center by bus (regularly).
ходить – to go on foot repeatedly:
- Я хожу в центр пешком. – I go to the center on foot (regularly).

In your sentence you first travel by transport (so ездить) and then on foot (so идти / ходить; here иду is chosen).

Why is it иду пешком and not хожу пешком, if this is also something I do every weekend?

This is a subtle point about style and viewpoint:

хожу пешком = “I (generally) go on foot / I usually walk” – a broad habit.
иду пешком = “(then) I walk (on that particular route / in that sequence).”

In По выходным я езжу… а потом иду пешком the speaker is describing each typical trip as a sequence:

I (each time) go by transport to the station,
and then (on that same trip) I walk.

So Russian often uses иду there, even though the whole sentence is about a habit, because we imagine each weekend’s trip step by step.
Хожу пешком would sound more like a general statement: “I usually walk (instead of using transport).”

Why is it в центр and not в центре?

The case shows direction vs location:

в центр – to the center (accusative, motion towards a place)
в центре – in the center (prepositional, location in a place)

Here you are moving towards the city center, so accusative is needed:

Я езжу в центр. – I go to the center.
Я живу в центре. – I live in the center.

What does до mean in до станции метро «Парк», and which case does it take?

До means “up to / as far as / until” in spatial or temporal sense.

It always takes the genitive case:

до станции – up to the station
до дома – up to (as far as) the house
до реки – up to the river

So станция (nominative) becomes станции (genitive) after до:

до станции метро «Парк» – as far as the metro station Park.

Why is it станции метро, not станция метро?

Because the preposition до requires the genitive, so:

Nominative: станция метро – (a/an) metro station
Genitive (after до): до станции метро – to the metro station

Only станции changes; метро is indeclinable (same form in all cases).

Why is the station name written as «Парк» and not just Парк or in parentheses?

In Russian, names of stations, films, newspapers, etc. are typically written in angle quotes:

станция метро «Парк»
станция метро «Охотный ряд»

This is similar to English “Park” but Russian typographic tradition prefers «…». In handwriting or plain text, people sometimes use "..." instead, but «…» is standard in print.

Why is there a comma before а потом?

Because а is a coordinating conjunction linking two clauses:

По выходным я езжу в центр до станции метро «Парк»,
а потом иду пешком.

In writing, Russian normally puts a comma before coordinating conjunctions (и, а, но, однако, зато, etc.) when they join two clauses (two separate “mini-sentences” with their own verbs: езжу and иду).

So the comma is mandatory here.

What is the difference between а and и here? Could I say и потом?

Both are possible, but they feel slightly different:

а потом – “and then” with a mild contrast / change of stage:
- First by transport, then (in contrast) on foot.
и потом – “and then” more neutrally, just adding another step.

In this sentence, а потом highlights a small shift: from going by transport to going on foot, so it’s very natural.
И потом would not be wrong, just a bit less expressive.

What exactly is пешком grammatically, and do I ever say на пешком?

Пешком is an adverb meaning “on foot / by walking”.

You do not use a preposition with it:

идти пешком – to go on foot
добраться пешком – to get there on foot

Using на пешком is incorrect. You can think of пешком as a single fixed word meaning “by walking”.