This passage is from The Children's Bach by Helen Garner
What is this, thought Vicki. What is in here? It is a warehouse, it has no walls or rooms. There is a row of windows, each one shaped like an eye with its brow raised. There is a TV, a phone on the floor, a bed like a big pink cloud. Where does she cook? Where does she wash herself? Where will I sleep? Everybody needs a bed. There are no walls or rooms.
Elizabeth turned round and saw her standing there beside her suitcase. She was ashamed. She turned down the music.
I search on net and found:
In here means the room or enclosed area (could be a field or something as was rightly pointed out) we're in
Does "What is in here?" mean:
What is this enclosed area?
What is in this place?