Al atardecer, buscamos un mirador desde el que se viera el mar.

Al atardecer means something like at dusk, toward evening, or as evening fell.

The al is the contraction of a + el. In this expression, atardecer is functioning as a noun-like expression meaning sunset / dusk / nightfall, so al atardecer is a very common way to say at dusk.

Learners sometimes notice that al + infinitive can also mean when doing something (for example, al entrar = when entering). That idea is close here too, because atardecer can also be understood as to grow dark. So the phrase has a natural sense of when it was getting dark.

Yes. Buscamos can mean either:

• we look for / we search (present)
• we looked for (preterite past)

These two forms are spelled the same in Spanish.

Here, the rest of the sentence makes the past meaning clear. The clause desde el que se viera el mar uses a past-time viewpoint, so buscamos is understood as we looked for.

This is very common in Spanish: sometimes only context tells you whether a form is present or preterite.

Both are possible in Spanish, but they give different shades of meaning.

• buscamos = we looked for
  This presents the action as a completed event.
• buscábamos = we were looking for / we used to look for
  This presents the action as ongoing, background, or habitual.

So:

• Al atardecer, buscamos un mirador...
  = At dusk, we looked for a viewpoint...
• Al atardecer, buscábamos un mirador...
  = At dusk, we were looking for a viewpoint...

The sentence you were given uses the more event-like, completed version.

A mirador is a viewpoint, lookout, or scenic viewing spot.

In Spain, this word is very common for:

• a terrace or platform built to enjoy the view
• a scenic point in a town, on a mountain, or by the coast
• sometimes even a part of a building with a good view

So un mirador is not just any place you stand; it usually suggests a place chosen or designed because of the view.

Because que by itself cannot work here after the preposition desde when it refers back to a noun.

The noun is un mirador, and the relative clause means from which the sea could be seen. In Spanish, this structure is:

• preposition + article + que

So:

• desde el que = from which

The el agrees with mirador, which is masculine singular.

Similar patterns are:

• la casa en la que vivo = the house in which I live
• el pueblo del que vengo = the town I come from
• la ventana por la que entró = the window through which he came in

So desde el que is the normal grammar here.

Yes, absolutely.

A very natural alternative is:

Al atardecer, buscamos un mirador desde donde se viera el mar.

That also means from where the sea could be seen.

The difference is mostly stylistic:

• desde el que sounds a bit more structured and explicitly linked to mirador
• desde donde sounds a bit more direct and conversational

Both are correct.

This is one of the most important grammar points in the sentence.

Spanish often uses the subjunctive in a relative clause when the noun being described is indefinite, not yet identified, wanted, searched for, or hypothetical.

Here, they were looking for a viewpoint with a certain characteristic:

• one from which the sea could be seen

They had not identified the viewpoint yet. It was something desired, not something already known and factual. That is why Spanish uses the subjunctive:

• buscamos un mirador desde el que se viera el mar

If the speaker were talking about a specific, real viewpoint already established as factual, the indicative would be more likely:

• Encontramos un mirador desde el que se veía el mar.
  = We found a viewpoint from which the sea could be seen.

So:

• subjunctive = desired / searched for / not yet identified
• indicative = known / real / factual

Because the main verb is in a past-time frame.

Spanish often follows a sequence of tenses:

• present/future main verb → present subjunctive often appears
• past main verb → imperfect subjunctive often appears

Compare:

• Buscamos un mirador desde el que se viera el mar.
  past framework
• Buscamos un mirador desde el que se vea el mar.
  present framework, meaning something like We’re looking for a viewpoint from which the sea can be seen

So viera is the past-side subjunctive form that fits the sentence.

Here se is not truly reflexive in the sense of the sea sees itself.

This is a very common Spanish structure that is passive-like or impersonal in effect. The idea is:

• se viera el mar = the sea could be seen
• or more naturally in English, from which you could see the sea

In this structure, el mar is the thing that is visible. You can think of it as similar to:

• Se ve la montaña. = The mountain can be seen / You can see the mountain.
• Se veían las luces. = The lights could be seen.

A useful clue is agreement:

• se viera el mar → singular, because el mar is singular
• se vieran las montañas → plural, because las montañas is plural

So the sentence does not mean the sea is doing the seeing; it means the sea is what could be seen.

Because Spanish often uses the definite article where English does not.

So Spanish says:

• el mar
• la playa
• el sol
• la luna

even in cases where English might simply say sea, beach, sun, or moon depending on context.

Here el mar means the sea in a general or contextually obvious sense: the sea visible from that viewpoint.

Also, mar is usually masculine in standard modern usage: el mar. You may occasionally see la mar, but that is more poetic, literary, or regional.

This is a normal and natural order.

Spanish often puts the subject after the verb in clauses like this, especially with se constructions:

• se viera el mar

That sounds very natural.

You could move things around in more literary or emphatic styles, but the given order is the standard one for this kind of sentence. It keeps the clause flowing smoothly after desde el que and sounds much more idiomatic than a more English-shaped arrangement.

Yes. A few natural alternatives are:

• Al atardecer, buscamos un mirador desde donde se viera el mar.
• Al atardecer, buscamos un sitio desde el que se viera el mar.
• Al atardecer, buscamos un mirador con vistas al mar.

They are all similar, but there are slight differences:

• desde donde / desde el que se viera el mar focuses on the idea of being able to see the sea from there
• con vistas al mar means with a sea view, which is a bit more compact and descriptive

The original sentence is perfectly natural, just a little more structured.