Learn Hardcore Icelandic: Mér finnst náttúran í sveitinni fallegri en húsin í borginni. - I find the nature in the countryside more beautiful than the houses in the city.

Finnast is a special verb in Icelandic that is often used impersonally to express opinions or feelings, similar to I think, I feel, or it seems to me.

Mér finnst literally means to‑me finds → it seems to me / I think / I find.
You cannot say Ég finnst. The verb finnast does not take a nominative subject like ég here; it takes an experiencer in the dative (here: mér).
Ég finn is a different verb form (the active verb finna, to find/feel/sense), used for things like Ég finn kulda (I feel cold) or Ég finn lykilinn (I find the key). It does not mean I think that something is pretty.

So you should learn Mér finnst … as a fixed expression for I think / I find (that) … when describing how something seems to you.

Why is mér in the dative case instead of ég in the nominative?

In Icelandic, certain verbs take their “subject-like” person in a case other than nominative. Finnast is one of these verbs.

Ég is nominative.
Mér is the dative form of ég.

With finnast used in this opinion/feeling meaning:

The thing being judged (here náttúran í sveitinni) is in the nominative.
The person who feels or thinks this (here mér) is in the dative.

So the structure is roughly:

Mér (to me, dative)
finnst (seems / I find)
náttúran í sveitinni fallegri … (the nature in the countryside [is] more beautiful …)

This is similar to other Icelandic sentences like:

Mér líkar þetta. – I like this (literally: this pleases me).

What is the grammatical subject of this sentence?

Grammatically, the subject is náttúran (í sveitinni).

In Icelandic:

The logical experiencer (mér) is in the dative and behaves like an indirect object.
The thing that is found / seems (náttúran í sveitinni) is in the nominative and is the real subject.

You can see this more clearly if you change the word order:

Náttúran í sveitinni finnst mér fallegri en húsin í borginni.

Here, náttúran í sveitinni is clearly in the subject position before the verb, and it controls agreement of the predicate adjective fallegri (more beautiful).

Why is it náttúran and not just náttúra?

The ending -an is the definite article attached to the noun.

náttúra = nature (indefinite)
náttúran = the nature (definite)

Icelandic normally attaches the definite article to the end of the noun instead of using a separate word like English the.

Here, náttúran í sveitinni corresponds to English the nature in the countryside, so the definite form is natural. We are talking about the nature there in general, not just some unspecific “nature”.

What do the endings -inni in sveitinni and borginni mean?

The ending -inni combines two things:

Dative case
Definite article (the)

Base forms:

sveit = countryside
borg = city

Dative singular definite:

sveitinni = in the countryside
borginni = in the city

They are in the dative because of the preposition í (see next question), and they are definite because we mean the countryside and the city in a general but specific way, similar to English usage in the countryside / the city.

Why is the preposition í followed by the dative here? When would it use the accusative?

The preposition í (“in / into”) can take either dative or accusative, depending on the meaning:

Dative = location (where something is)
Accusative = movement into (where something is going)

In the sentence:

í sveitinni = in the countryside → location → dative (sveitinni)
í borginni = in the city → location → dative (borginni)

Examples to contrast:

Ég er í borginni. – I am in the city. (dative, location)
Ég fer í borgina. – I am going to the city / into the city. (accusative, borgina)

What is húsin exactly? Why not just hús?

The basic noun is hús (house), which is neuter.

Neuter nouns often have the same form for singular and plural in the indefinite nominative:

Singular nominative: hús – a house
Plural nominative: hús – houses

You only clearly see the number in the definite forms:

Singular definite: húsið – the house
Plural definite: húsin – the houses

In the sentence we are comparing the nature with the houses in the city, so we need:

húsin í borginni = the houses in the city (plural, definite).

Why is the adjective fallegur changed to fallegri? Why not use something like meira falleg?

Fallegri is the comparative form of the adjective fallegur (beautiful).

In Icelandic, comparatives are normally made by changing the adjective itself, not by using an extra word like more:

fallegur → fallegri – beautiful → more beautiful
skemmtilegur → skemmtilegri – fun → more fun
góður → betri – good → better (irregular)

So:

fallegri en … = more beautiful than …

The construction meira falleg is not idiomatic; you should almost always use the inflected comparative form (fallegri, skemmtilegri, betri, etc.) instead of meira + adjective.

Does fallegri agree with náttúran or with húsin, or with both?

Grammatically, fallegri is the predicate adjective that agrees with náttúran (í sveitinni), because that is the subject of finnst.

The underlying structure is:

Mér finnst [náttúran í sveitinni] [fallegri] [en (hvað?) húsin í borginni].

So we are saying:

To me the nature in the countryside is more beautiful (than the houses in the city are).

The part en húsin í borginni (than the houses in the city) is only giving the comparison standard; it does not force fallegri to agree with it. The agreement is between fallegri and náttúran.

What exactly does en mean here? Is it the same en as but?

Yes, en can have two main uses:

en = than in comparisons
- fallegri en húsin í borginni – more beautiful than the houses in the city
en = but in contrasts
- Ég kom, en hann fór. – I came, but he left.

In your sentence, en clearly has the comparative meaning than because it follows a comparative adjective (fallegri). Context and structure tell you which meaning is intended.

Should the nouns after en stay in the same case as before, or does en change the case?

With simple comparisons using en + a noun, the compared nouns usually stay in the same case; en itself does not change the case.

Here:

náttúran (subject) = nominative
After en, we have húsin (also nominative).

You can think of it as if the second part is “short for” a full clause:

Mér finnst náttúran í sveitinni fallegri en húsin í borginni (eru).
I think the nature in the countryside is more beautiful than the houses in the city (are).

So húsin would be the subject of the implied verb eru, so it is nominative as well.

Can I change the word order, for example: Náttúran í sveitinni finnst mér fallegri en húsin í borginni?

Yes, that word order is possible and correct:

Náttúran í sveitinni finnst mér fallegri en húsin í borginni.

This version:

Puts the subject náttúran í sveitinni first (more “neutral” subject–verb order).
Keeps mér right after the verb finnst, still in the dative.

Both orders are natural:

Mér finnst náttúran í sveitinni fallegri en húsin í borginni. (emphasis on me, my opinion)
Náttúran í sveitinni finnst mér fallegri en húsin í borginni. (more neutral, emphasis on the nature)

Could I express a similar idea with líka, as in Mér líkar náttúran í sveitinni betur en húsin í borginni? What is the difference?

Yes, Mér líkar … betur en … is another natural way to express preference:

Mér líkar náttúran í sveitinni betur en húsin í borginni.
≈ I like the nature in the countryside better than the houses in the city.

Main differences:

Mér finnst X fallegri en Y focuses on your judgment of beauty (X seems/is more beautiful than Y).
Mér líkar X betur en Y focuses on your personal liking or preference (I like X better than Y).

In many contexts they may both be appropriate, but Mér finnst … fallegri … is more about how beautiful something appears, while Mér líkar … betur … is more about what you prefer or enjoy.