"There is a bank over there."
Translation:Di situ ada bank.
why not: bank ada di sana
'bank ada di sana' = 'The bank is there'.
'di sana ada bank' = 'There is a bank (over there)'
In the first sentence, it's about the location of a specific bank ('The bank', not just 'a bank').
In the second sentence, the focus/emphasis is on the location, no matter which bank.
That's probably the reason that the English sentence uses an extra phrase 'over there'.
That's not really any explanation, because there was a lot of sentences before that had "to be" in English but not in Indonesian. And there was even a remark that "to be" words in Indonesian are usually not needed. So the question still stands: Why is it suddenly needed in this context in particular and not in others?