Taking the existential sentence:
There was food.
The existential question form would be:
Was there food?
There was a house on a high hill ⇒ Was there a house on a high hill?
There were many fruit trees surrounding the house ⇒ Were there many fruit trees surrounding the house?
The same is true for verbs other than "to be", although this structure can seem overly formal, dramatic, and/or literary (although the existential statement itself is already somewhat literary):
There lived in that house an old man and an old woman ⇒ Lived there in that house an old man and an old woman?
More common would be:
Did an old man and an old woman live there, in that house?
That being said: It's not uncommon to hear an existential phrase spoken as a question, to indicate the speaker believes the statement is true:
A: I went to the meeting last night. It was incredibly boring.
B: There was food?
A: Yes, at least there was food.
It's also possible to phrase the question as in your second example:
A: Last night I went to this meeting -
B: Where there was food?
A: Yes, there was food at the meeting. But it was so boring it wasn't really worth it.
Again, this are both slightly literary. Simple questions are more common:
Was there food (there)?