[Di situ] ==> There/Over there (location).
[ada] ==> is the presence of.
[bank] ==> a bank.
'Over there is the presence of bank' ==> 'There is a bank (over there).'
In the Indonesian sentence, the location indicator is placed at the beginning of the sentence for emphasis.
It's about the location, not about the bank, so it doesn't matter which bank, as long as it is a bank.
If you're looking for the location of a bank :
Di mana ada bank? = Where is a bank?
Di sana ada bank. = (over) There is a bank.