Learn Hardcore Portuguese (Portugal): Se bem que a ilha seja pequena, há muito para descobrir se caminharmos com calma. - Although the island is small, there is a lot to discover if we walk calmly.

Se bem que is a bit more idiomatic and can sound slightly more colloquial or conversational, especially in European Portuguese.
Embora is very common and slightly more neutral/formal.

In this position (at the start of the sentence), both normally take the subjunctive (seja).

Why is it seja and not é after a ilha?

Because Se bem que (like embora) usually takes the subjunctive mood when it introduces a concessive clause.

General pattern:

Se bem que / Embora
- subjunctive
  Se bem que a ilha seja pequena…
  Embora a ilha seja pequena…

This resembles English patterns like:

Although the island may be small…
Even though the island is small…

In Portuguese, the concession-triggering conjunction (se bem que, embora) is what normally forces the subjunctive (seja), not the tense or time reference itself.

Can you ever say Se bem que a ilha é pequena, with the indicative?

Yes, but it is used differently.

At the beginning of a sentence (like in your example), standard grammar strongly prefers the subjunctive:
- Se bem que a ilha seja pequena, há muito para descobrir… ✅ (preferred)
After the main clause, se bem que can behave more like a parenthetical comment, and the indicative is common:
- Há muito para descobrir na ilha, se bem que a ilha é pequena.
  = There is a lot to discover on the island, although the island is small.

In that afterthought position, many native speakers will use é instead of seja in casual speech. At the beginning, though, seja is the more natural and taught form.

What is the role of há in há muito para descobrir, and why not tem?

Here há is the impersonal verb haver with an existential meaning: there is / there are.

Há muito para descobrir ≈ There is a lot to discover / There is much to discover.

In European Portuguese:

haver (há) is the standard verb for this existential sense.
Using ter existentially (tem muito para descobrir) is more characteristic of Brazilian Portuguese and is usually not considered standard in Portugal (though people may understand or occasionally use it informally).

So in European Portuguese, há muito para descobrir is the natural, correct form.

Why is it muito para descobrir and not something like muito por descobrir or muito a descobrir? Do these change the meaning?

All three exist, but they are not identical.

muito para descobrir
- Focus: there is a lot available to be discovered / for you to discover.
- Very neutral and common:
  - Há muito para fazer. – There is a lot to do.
  - Há muito para ver na cidade. – There is a lot to see in the city.
muito por descobrir
- Often carries a nuance of still not done / yet to be discovered:
  - Ainda há muito por descobrir. – There is still a lot left to discover.
- Slightly more emphatic about the fact that it remains undone.
muito a descobrir
- Also possible, and often similar to para descobrir, but in European Portuguese para descobrir is more common in this kind of phrase.

In your sentence, há muito para descobrir is the most straightforward and natural-sounding choice.

What is the function of se in se caminharmos com calma? Is it the same se as in Se bem que?

They are different uses of se:

In Se bem que, se is part of a fixed expression:
- Se bem que = although / even though (a concessive conjunction).
In se caminharmos com calma, se is the usual conditional if:
- se caminharmos com calma = if we walk calmly / if we go slowly

So:

Se bem que works as a single unit: a conjunction meaning although.
The second se is the normal if that introduces a condition.

Why is it caminharmos after se, and not caminhamos?

Because se caminharmos uses the future subjunctive, which is standard in Portuguese for real or possible future conditions introduced by se.

Conjugation of caminhar (future subjunctive):

se eu caminhar
se tu caminhares
se ele / ela caminhar
se nós caminharmos
se vós caminhardes
se eles / elas caminharem

So se caminharmos com calma literally means if we should walk / if we walk (in the future) calmly.

In Portuguese, after se with an if meaning referring to the future, you normally use the future subjunctive, not the present indicative:

✅ Se caminharmos com calma, vamos descobrir muito.
❌ Se caminhamos com calma, vamos descobrir muito. (sounds wrong in standard Portuguese)

Could you replace caminharmos with another verb like andarmos, and what would change?

Yes, you could say:

Se andarmos com calma…

Differences:

caminhar focuses more on walking as such, often used for walking/hiking or going on foot in a more deliberate way.
andar is more general (to walk / to go / to move around), and can have broader meanings (to go around, to be walking about, to be moving).

In this sentence:

Se caminharmos com calma suggests something like if we go walking calmly / if we walk around slowly, with a slight nuance of exploring on foot.
Se andarmos com calma is also correct, but a bit more neutral; it might sound slightly less like a purposeful hike and more like simply moving around calmly.

Both are acceptable; context and style preference decide.

What does com calma literally mean, and could I just say devagar instead?

Literally, com calma means with calmness.

Nuance:

com calma can mean without rushing, in a relaxed way, not just physically slow but also mentally unhurried.
devagar means slowly, focusing more on speed.

In this sentence:

se caminharmos com calma → if we walk calmly, taking our time, relaxed.
se caminharmos devagar → if we walk slowly (emphasis on slow pace).

In practice, you can say:

Se caminharmos devagar, há muito para descobrir.

It is perfectly correct; it just focuses a bit more on the speed of walking and a bit less on the idea of not rushing / being relaxed.

Is the comma after pequena obligatory?

Yes, in standard written Portuguese it is expected here.

Structure:

Subordinate concessive clause first:
Se bem que a ilha seja pequena,
Main clause after:
há muito para descobrir se caminharmos com calma.

When a subordinate clause (introduced by se bem que, embora, quando, etc.) comes before the main clause, it is normally separated by a comma:

Embora esteja frio, vamos dar um passeio.
Se tiveres tempo, passa cá em casa.

So:

Se bem que a ilha seja pequena, há muito para descobrir… ✅
Se bem que a ilha seja pequena há muito para descobrir… ❌ (punctuation feels off)

How might a Brazilian Portuguese speaker say this? Are there notable differences?

A natural Brazilian version could be:

Embora a ilha seja pequena, ainda há muito o que descobrir se caminharmos com calma.

Notable differences:

Conjunction:
- Embora is extremely common in Brazil; se bem que is used too but often with a slightly different, more conversational nuance (sometimes almost like though in English).
Existential verb:
- In Brazil, people often say:
  - Tem muito o que descobrir. (very common in speech)
- This tem as there is / there are is widespread in Brazilian Portuguese, though há is also correct and more formal.
Structure after muito:
- Brazilians often say:
  - muito o que descobrir instead of muito para descobrir.

So a very typical Brazilian-sounding sentence might be:

Embora a ilha seja pequena, tem muito o que descobrir se caminharmos com calma.

Your original sentence is clearly European Portuguese in flavor, especially because of há muito para descobrir.

How do you pronounce ilha and caminharmos, especially the lh and nh sounds?

In European Portuguese:

lh in ilha
- ilha is roughly EE-lyah (in one smooth word).
- The lh sound is a palatal lateral (like a softer ly sound).
- Similar to the lli sound in English million or the ll in Spanish calle, but a bit shorter and tighter.
nh in caminharmos
- caminharmos is roughly kah-mee-nyar-moosh (European Portuguese often has a final -s pronounced like English sh).
- The nh sound is a palatal nasal (like ny).
- Similar to the ni sound in English onion or the ñ in Spanish niño.

So:

ilha → EE-lyah
caminharmos → kah-mee-nyar-moosh

The key is to join lh as a single ly-type sound and nh as a single ny-type sound, not as separate l + h or n + h.