Por la tarde visitamos la catedral y luego subimos al castillo que está en la parte alta de la ciudad.

In Spain, por la tarde is the normal way to say in the afternoon.

• por la mañana = in the morning
• por la tarde = in the afternoon / in the evening
• por la noche = at night / in the evening

A native English speaker often expects en, because in often translates as en, but with parts of the day Spanish usually uses por in this expression.

In some parts of Latin America, en la tarde can be heard, but for Spain, por la tarde is the standard choice.

Both visitamos and subimos can be either:

• present: we visit / we go up
• preterite: we visited / we went up

In this sentence, they are understood as preterite because the sentence tells a completed sequence of events in the past:

• Por la tarde visitamos la catedral
• y luego subimos al castillo

The time expression and the context make it clear that this is a finished past action.

This is very common in Spanish: with nosotros, some -ar and -ir verbs have the same form in the present and preterite.

No. The verb visitar normally takes a direct object directly, without a preposition.

So you say:

• visitamos la catedral
• visité el museo
• van a visitar Toledo

You only use the personal a before a specific person, or sometimes a personified being:

• visitamos a nuestros abuelos
• visité a María

But la catedral is a thing/place, so there is no a.

Because al is the contraction of a + el.

• a = to
• el castillo = the castle
• a el castillo becomes al castillo

This contraction is mandatory in standard Spanish whenever a is followed by el:

• vamos al hotel
• subimos al castillo
• llegaron al aeropuerto

The only common exception is when El is part of a proper name, such as a El Escorial.

Yes. Subir means to go up, to climb, or to ascend.

Here it makes sense because the castle is in the upper part of the city, so they physically go upward to reach it.

So subimos al castillo can be understood as:

• we went up to the castle
• we climbed up to the castle

It sounds very natural in Spanish when talking about a place on higher ground.

Both can mean then / afterwards / later.

So these are both natural:

• y luego subimos al castillo
• y después subimos al castillo

In this sentence, luego simply links the events in sequence: first they visited the cathedral, then they went up to the castle.

In Spain, luego is very common in narration. Depending on context, luego can also mean later, but here it clearly means then / afterwards.

Because que introduces a relative clause describing el castillo:

• el castillo que está en la parte alta de la ciudad
• the castle that is in the upper part of the city

This is the most neutral and straightforward structure.

You could also hear el castillo, que está... with commas if it were extra information, but here it is likely identifying which castle we mean.

Donde is possible in some rephrasings, but not in the same structure:

• subimos al castillo, que está en la parte alta de la ciudad
• subimos al castillo, donde... would change the meaning and structure

So que está is the normal choice for that is.

Because Spanish uses estar for location.

So:

• La catedral está en el centro
• El castillo está en la parte alta
• Madrid está en España

Even though location may be permanent, Spanish normally uses estar, not ser, when saying where something is.

So que está en la parte alta de la ciudad means that is located in the upper part of the city.

Literally, it means the high part of the city or the upper part of the city.

A more natural English translation might be:

• the upper part of town
• the high part of the city
• the city’s upper area

This often refers to the area on a hill or higher ground.

So the sentence suggests that the castle is above the lower part of the city, which also explains why subimos is a good verb here.

Because la parte alta de la ciudad is a possessive-type structure: the upper part of the city.

Spanish often uses de where English uses of:

• el centro de la ciudad = the city centre
• la parte vieja de la ciudad = the old part of the city
• la parte alta de la ciudad = the upper part of the city

If you said en la ciudad, that would mean in the city, which is a different idea.

Yes, it could go elsewhere, but putting it first is very natural because it sets the scene.

• Por la tarde visitamos la catedral...
• Visitamos la catedral por la tarde...

Both are correct.

Starting with Por la tarde helps organize the story by giving the time frame first. This is very common in Spanish narration.

Spanish often uses the definite article when referring to well-known, specific places in a town or city.

So la catedral and el castillo suggest:

• the cathedral of that city
• the castle of that city

Even if English might sometimes omit that sense or use a in a looser description, Spanish often prefers the when the place is understood to be specific and identifiable.

Not here. Subir a a place means to go up to that place.

So:

• subimos al castillo = we went up to the castle

If you wanted to say we climbed the castle, that would sound odd in most contexts, and Spanish would usually need a different structure depending on the exact meaning.

Here the idea is movement toward a higher location, not climbing on the walls of the castle itself.