i understand that native speakers would say:
I'm going to the bank.
I'm going to the park.
I'm going to the hospital. (american english)
"the" is used when there is only one bank, park, etc where you are or when it is understood which specific bank, park, etc is being referred to. what would you say in the following situations?
1. Somebody asks me when i am in town. S/he says, "where can i cash my traveler's checks?"
situation: There are several banks in town.
you should state the situation before asking your question.
is it possible to say, "you can cash them at a bank,"

Or "you can cash them at the bank,"

Or "you can cash them at banks."

?
if you tell me "at the bank", i will ask you 'at which bank?' because i might think that only one bank cashes travelers checks.
2. I say to a friend of mine, "let's make some sandwiches, go to a park, and eat them."

Situation: There are several parks near my house. I haven't decided which one to go to.
4. I say to somebody, "your wife was taken to a hospital."
then your friend will ask you "which hospital?' or 'what is the name of the hospital?'
situation: There are several hospitals around here.