Bu eski yapı yüzyıllarca şehrin simgesi oldu.

Bu means this.

Turkish does not have articles that work like English a/an and the. So in a phrase like bu eski yapı, bu already tells you the noun is specific: this old structure/building.

In many Turkish sentences, whether something is a or the is understood from context rather than from a separate word.

In Turkish, demonstratives and adjectives normally come before the noun.

So:

• bu = this
• eski = old
• yapı = structure/building

Together: bu eski yapı = this old structure

This is the normal order:

• bu güzel ev = this beautiful house
• o büyük şehir = that big city

Also, Turkish adjectives do not change form for singular/plural or gender, so eski stays eski.

Yapı is a fairly broad word meaning structure, building, or constructed thing.

It is often a bit broader or more formal than bina, which usually means building more directly.

So in this sentence, yapı can suggest something like:

• a structure
• a building
• an edifice
• possibly a historic construction

A learner might translate it as building, but structure is often closer to the Turkish nuance.

Yüzyıllarca is built from:

• yüzyıl = century
• -lar/-ler = plural
• -ca/-ce (here -ca) = a suffix that can give a sense like for many ..., throughout ..., or as much as ...

So yüzyıllarca means for centuries or for many centuries.

This suffix is very common with time words:

• yıllarca = for years
• aylarca = for months
• günlerce = for days

So Turkish does not need a separate word like English for here.

This happens because şehir is one of the words that often loses its second vowel before a vowel-initial suffix.

So:

• base form: şehir = city
• genitive suffix: -in
• expected by simple addition: şehir + in
• actual form: şehrin

This is a common sound change in Turkish.

You can compare:

• şehir → şehri = the city (object form)
• şehir → şehrin = of the city / the city’s
• şehir → şehre = to the city

So şehrin is the correct genitive form.

Because simgesi contains the 3rd person possessive suffix.

Breakdown:

• simge = symbol
• simge-si = its symbol / the symbol of it

In Turkish, when you say X’in Y’si, the second noun usually takes a possessive suffix.

So:

• şehrin simgesi literally = the city’s symbol
• more naturally = the symbol of the city

Also notice the extra s in simge-si. That s appears because the noun ends in a vowel.

Turkish usually expresses this idea with a genitive + possessive structure.

Pattern:

• X-in Y-si = Y of X / X’s Y

Here:

• şehrin = of the city / the city’s
• simgesi = its symbol / symbol

So:

• şehrin simgesi = the city’s symbol
• or the symbol of the city

English uses of very often. Turkish usually does not. Instead, it marks the relationship with suffixes on both nouns.

Oldu is the past tense of olmak, which often means to become or to be in certain constructions.

Here, şehrin simgesi oldu can carry the sense of:

• became the symbol of the city
• or, depending on context, was the symbol of the city / served as the symbol of the city

That is why this form may feel a little broader than a simple English was.

In historical or descriptive sentences, oldu can suggest that something came to hold that role or ended up functioning that way.

Because Turkish normally places the finite verb at the end of the sentence.

So the structure here is roughly:

• Bu eski yapı = subject
• yüzyıllarca = time expression
• şehrin simgesi = predicate/complement
• oldu = verb

This final-verb pattern is one of the most important features of Turkish word order.

English speakers often expect the verb earlier, but in Turkish, verb-final order is the default.

Yes, that is also possible.

• şehrin simgesiydi = it was the symbol of the city
• şehrin simgesi oldu = it became / came to be / served as the symbol of the city

The difference is mainly one of nuance:

• simgesiydi is a more direct statement of a state: it was
• oldu can sound a little more dynamic or result-oriented: it became, it came to be, or it served as

In some contexts, both could be translated similarly in English, but the Turkish wording is not exactly identical in feel.

Because eski is an adjective, and Turkish adjectives are very simple in this respect.

They do not agree with the noun for:

• gender
• number
• case

So you get:

• eski yapı = old structure
• eski yapılar = old structures
• eski yapının = of the old structure

The adjective eski stays the same every time. The suffixes go on the noun, not the adjective.