In this test question I am not sure why it is escrita?

Question

Otra obra famosa es el Cantar de Mio Cid, escrita en el siglo XIII.

I guessed this correctly but when I clicked on the explanation of past participle examples in Spanish it did not explain why it is escrita?

Can someone please explain?

Accepted Answer

Hola LIA
Yes, as David said, the past participle is used in this case both in Spanish and English. The form "escrito" is the past participle (irregular) of "escribir" and it needs to agree with the noun it's referring to, in this case the feminine noun "obra". They act as adjectives as explained in the lesson. 
If we use them as part of a perfect tense with the verb haber, for example: "hemos escrito un libro", then the past participle doesn't change, it's always the masculine singular form.
I hope this clarified it.
Saludos cordiales
Inma

Answer

This looks like a reduced relative clause and is exactly the same as in English.

Otra obra famosa es el Cantar de Mio Cid, ( que fue) escrita en el siglo XIII.

Another example is el Cantar de Mio Cid, ( which was ) written in the 18th Century