Learn Hardcore Spanish (Latin America): Ese castillo es del siglo XV.

este castillo = this castle (close to the speaker)
ese castillo = that castle (a bit farther from the speaker, or close to the listener)
aquel castillo = that castle over there / that distant castle (far from both speaker and listener, or “mentally distant”)

In Latin America, ese is very common and often used for most “non-near” things; aquel tends to sound more formal, literary, or emphatic, and is used less in everyday speech.

So Ese castillo es del siglo XV basically means That castle (not right here next to me) is from the 15th century.

Why ese and not esa?

Spanish adjectives must agree in gender and number with the noun:

castillo ends in -o and is masculine singular.
The matching demonstrative is ese (masculine singular).

Other forms:

ese castillo (that castle)
esa casa (that house – feminine singular)
esos castillos (those castles – masculine plural)
esas casas (those houses – feminine plural)

Why is it del siglo XV and not de el siglo XV?

In Spanish, de + el always contracts to del:

de el siglo XV → del siglo XV
de el profesor → del profesor

This is mandatory; de el (separate) is considered incorrect in standard written Spanish.

The same happens with a + el → al (for example, al castillo instead of a el castillo).

Why is there an article: del siglo XV instead of just de siglo XV?

Spanish normally uses the definite article with centuries:

el siglo XV = the 15th century
en el siglo XXI = in the 21st century

So you say:

Ese castillo es del siglo XV.
Fue construido en el siglo XV.

Without the article (de siglo XV) sounds wrong or at best very odd in standard Spanish.

How do you read siglo XV in Spanish? Is it the 1400s or the 1500s?

You normally read XV as a regular number:

siglo XV → siglo quince (15th century)

It refers to the years 1401–1500, just like in English:

siglo XV = 15th century = the 1400s (not the 1500s)

You will also see it written in digits as siglo 15, but the pronunciation is the same: siglo quince.
More formal, but less common, would be siglo decimoquinto.

What exactly does de express in es del siglo XV?

Here de expresses origin or time period. It’s similar to saying from the 15th century in English.

Some parallel examples:

Es de México. = He/She/It is from Mexico.
Es de madera. = It’s (made) of wood.
Es del siglo XV. = It’s from the 15th century.

So ser + de can describe origin, material, or historical period.

Why do we use es and not fue in this sentence?

Es del siglo XV uses present tense because we’re describing a timeless characteristic of the castle: its historical origin.

Ese castillo es del siglo XV.
→ That’s what it is (its identity / classification), even today.

If you say:

Ese castillo fue construido en el siglo XV.
→ It was built in the 15th century (focus on the event in the past).

Both are correct, but they highlight different things:

es del siglo XV = classification / origin
fue construido en el siglo XV = the act of building (past event)

Could I say Ese castillo es siglo XV without del?

No, not in standard Spanish. You need de + article:

✅ Ese castillo es del siglo XV.
❌ Ese castillo es siglo XV.

You might sometimes hear something like Es muy siglo XV in a joking or metaphorical way (like “It’s so 15th-century”), but that’s a different, stylistic use.

Is there any difference between siglo XV and siglo quince in speech?

When speaking, siglo XV is normally pronounced exactly as siglo quince. You don’t spell out the Roman numerals; you just say the number:

Written: siglo XV
Said: siglo quince

You can also write siglo 15, which you would still say siglo quince.
In everyday conversation, both spellings refer to the same thing; Roman numerals are more common in formal writing, history books, etc.

How do you pronounce castillo and siglo (especially ll) in Latin America?

Approximate pronunciations:

castillo ≈ kahs-TEE-yo or kahs-TEE-jo
siglo ≈ SEE-glo

The ll in castillo varies by region:

In many parts of Latin America: ll sounds like English y in yes → [kaˈstiʝo] / [kaˈstiyo]
In some areas of Argentina, Uruguay, and a few others: ll can sound like sh in she or zh → [kaˈstiʃo] / [kaˈstiʒo]

Both are understood throughout the Spanish-speaking world.

Can I move del siglo XV and say Ese castillo del siglo XV es muy famoso?

Yes, that’s correct and natural, but the structure changes slightly:

Ese castillo es del siglo XV.
→ That castle is from the 15th century. (simple statement about time period)
Ese castillo del siglo XV es muy famoso.
→ That 15th‑century castle is very famous.
(Here del siglo XV works like an adjective phrase modifying castillo.)

Both are fine; you just add more information to the noun in the second version.

In Latin America, would people say aquel castillo instead of ese castillo?

They can, but ese is more common in everyday speech.

Rough guide:

ese castillo: normal, neutral “that castle”, not right next to the speaker.
aquel castillo: emphasizes greater distance (physical or emotional), or sounds a bit more formal/literary:
- Aquel castillo es del siglo XV. = That castle way over there is from the 15th century.

In many Latin American dialects, ese covers a wide range of “that,” and aquel is reserved for when you really want to stress distance or sound more elegant.