It’s not uncommon to see buildings like the one above dotting the Cambodian landscape….
They are distinctive for two things: first while they may have some vents, like the one above, they have no windows. And second, they have an opening like the one on the left end of the building (right photo) and birds are flying in and out.
You have heard of birdnest soup. This is where they get the birdnests. The birds nest in these rooms and create nests held together with their saliva, and then later the nests are harvested and soaked and made into soup.