La capital del norte no es tan grande como la del sur, pero tiene una muralla muy bonita.

Because de + el contracts to del in Spanish.

• de el norte → del norte
• This contraction is mandatory.

So la capital del norte means the capital of the north.

A useful contrast:

• de + la does not contract, so you say de la ciudad, not dela ciudad.

In this sentence, capital means capital city, and that noun is feminine in Spanish: la capital.

Examples:

• Madrid es la capital de España.
• La capital del norte...

Be careful: some words ending in -al are masculine, but grammatical gender in Spanish is not always predictable from the ending alone. Here, you simply learn it as la capital.

La del sur is a shortened way of saying la capital del sur.

Spanish often avoids repeating a noun if it is already clear.

So:

• La capital del norte no es tan grande como la capital del sur becomes
• La capital del norte no es tan grande como la del sur

Here, la stands in for la capital.

This is very common in Spanish:

• Mi casa es más grande que la de mi hermano. = My house is bigger than my brother’s house.

To compare equality or inequality with adjectives, Spanish uses:

• tan + adjective + como
• as ... as

So:

• tan grande como = as big as
• no es tan grande como = is not as big as

Examples:

• Es tan alto como su padre. = He is as tall as his father.
• No es tan interesante como parece. = It is not as interesting as it seems.

English speakers often want to use que, but after tan + adjective, the correct word is como.

Both can express a similar idea, but no es tan grande como is much more natural.

• no es tan grande como = it is not as big as
• es menos grande que = literally it is less big than

Spanish usually prefers:

• más ... que for more ... than
• menos ... que for less ... than
• tan ... como for as ... as

But with grande, menos grande can sound a bit awkward in many contexts. Native speakers would normally say:

• No es tan grande como... or
• Es más pequeña que... if appropriate.

Because como here is a comparison word, not a question or exclamation word.

• tan grande como = as big as → no accent
• ¿Cómo estás? = How are you? → accent: cómo

So:

• como = as / like / I eat depending on context
• cómo = how

The accent helps distinguish meanings.

Because Spanish uses tener to say that a place has something.

• tiene una muralla = it has a wall
• es una muralla would mean it is a wall, which is completely different.

So the structure is:

• [place] + tiene + noun

Examples:

• La ciudad tiene un castillo.
• El pueblo tiene una plaza muy bonita.

Both relate to walls, but they are not the same.

• muro = a wall in general
• muralla = a city wall, defensive wall, rampart

In this sentence, muralla suggests a historic defensive wall around a town or city, which fits the context much better than muro.

So una muralla muy bonita sounds like:

• an old fortified wall
• a scenic or historic city wall

In Spanish, adjectives usually come after the noun.

• una muralla muy bonita
• noun: muralla
• adjective phrase: muy bonita

This is the normal word order.

Also:

• muy = very
• bonita agrees with muralla, which is feminine singular

So:

• muralla → feminine singular
• adjective must match → bonita, not bonito

Bonita is a very common, natural adjective meaning pretty / lovely / beautiful.

• bonita is everyday and very idiomatic
• bella also means beautiful, but it often sounds a bit more literary or elevated
• buenita does not mean beautiful; it usually means something like nice, kind, or sometimes rather good depending on context

So una muralla muy bonita is a very natural way to say that the wall is attractive or lovely.

Because some adjectives change form for gender, and some do not.

• bonito / bonita / bonitos / bonitas changes
• grande does not change for gender in the singular

So:

• la capital ... grande
• una muralla ... bonita

Examples:

• un pueblo bonito
• una ciudad bonita
• un edificio grande
• una plaza grande

Both adjectives must agree in number, but only some show a masculine/feminine difference.

Because pero introduces a contrast, and in Spanish it is very common to place a comma before it when joining two clauses.

Here the sentence has two parts:

• La capital del norte no es tan grande como la del sur
• pero tiene una muralla muy bonita

The comma helps separate the two contrasting ideas:

• it is not as big
• but it has a very সুন্দর feature

This is similar to English punctuation before but.

Yes. In this sentence, norte and sur are lowercase because they are being used as common directional/geographical terms, not necessarily as official proper names.

So:

• del norte
• del sur

Spanish often writes compass directions in lowercase unless they are part of an official name.

Examples:

• el norte de España
• el sur de Francia

But in a proper name, capitalization may appear:

• América del Sur

It uses ser: no es tan grande.

Spanish uses ser for characteristics such as size, identity, and general qualities.

Here, grande describes a characteristic of the capital, so ser is the correct verb:

• es grande
• no es tan grande como...

You would not normally use estar grande here. Estar is used for states, conditions, or location, not this kind of general comparison.

Yes, la capital norteña is possible, but it is not exactly the same in tone.

• la capital del norte = the capital of the north
• la capital norteña = the northern capital

Del norte is more straightforward and neutral.
Norteña is more descriptive and may sound slightly more stylistic or regional depending on context.

For a learner, la capital del norte is the safest and most transparent option.