Learn Farsi: گفته می‌شود که این ویرانه یک نفرین تاریک دارد.

Literally, it means 'It is said that'. It is an impersonal passive verb. To form the present passive, you take the past participle of the main verb (gofte, from goftan, to say) and add the present tense of shodan (to become). Because it is 'impersonal' (meaning 'it' is the general subject), we use the third-person singular form: mi-shavad.

In English, we say 'is said TO HAVE', using an infinitive. Why does Farsi use dārad (it has) instead?

Farsi rarely uses infinitives the way English does to connect thoughts. Instead, it uses ke (that) followed by a fully conjugated verb. So rather than saying 'This ruin is said to have...', Farsi phrases it as 'It is said that this ruin has...' (gofte mi-shavad ke... dārad).

Doesn't the word ke usually force the next verb into the subjunctive mood? Why is dārad in the normal indicative mood?

Great catch! While ke often triggers the subjunctive (like after wanting or suggesting), reporting verbs are an exception. When you report a statement, belief, or fact using phrases like gofte mi-shavad ke (it is said that) or shenide mi-shavad ke (it is heard that), the following verb stays in the indicative mood because you are describing something presented as an existing reality.

I recognize virān as meaning 'destroyed'. What does the suffix in virāne do?

Adding the -e suffix to the end of the adjective (destroyed or ruined) turns it into a noun. So simply means 'a ruin' or 'a destroyed place'. This is a very common way to create nouns from adjectives in Farsi.