Learn Italian: Il faro più antico si trova in Sardegna. - The oldest lighthouse is located in Sardinia.

Large islands act exactly like countries and regions in Italian. While they do require a definite article in most grammatical roles (like La Sardegna è bellissima), they drop the article when paired with the preposition in to express location or destination. You simply say in Sardegna. By contrast, small standalone islands express location using the preposition a (like a Capri).

Why use the reflexive verb si trova instead of just è for "is located"?

While you can absolutely say è in Sardegna, using trovarsi (literally "to find oneself") is much more common and idiomatic in Italian for expressing where a building, city, or geographical landmark is situated.

In English we put "oldest" before "lighthouse". Could I write Il più antico faro?

Yes, you can, but placing the superlative adjective after the noun (Il faro più antico) is the standard and most natural word order in Italian. Notice that the single definite article Il at the beginning covers the whole phrase; you do not need to add another article before più.

Why use antico instead of vecchio for "oldest"?