Cardboard box with outer layer pulled off.
Printed floor pattern.
Antennae from a VvV vehicle
Chimney: Marker cap with missile tip
Ventilation system: Corps and Charbroil backpacks with stir straw
Door: Wood with printed sign and Snake Eyes v. 3 sword hilts for doorknobs
Vent above the door: Legos
"Keep Away" safety cone: gumball machine
Table: wood and dowel rod
Oil drums: PTE

This started as a Custom Celebration Two Week Shoebox Diorama Challenge entry. My idea was to think "inside the box" and use the corrugated inner layer for the outside of a Quonset hut like the one used in issue #2 of the Marvel GI Joe series, where the Joes first encounter Kwinn.

I ran out of time for the challenge but got it far enough along that it had to be completed. I can see this structure working in several different environments which is why one side has windows and the other side doesn't.

In real life Quonset huts are cheap and since they are mostly prefabricated, quick and easy to set up. The military likes to use them for everything from barracks to communication centers to aircraft hangers.