Ruined Space Marine City Part 1
What you need: Foam board
Knife
Blue paint
Clear tape
Pva glue
First thing you do is cut a piece of foam board out for the top of bunker(make big enough for anything you want to put in it.) Then, paint the top whatever chapter you want(I did ultramarines.) After it dries, it should look like this

now cut out the rest off the walls to fit the roof, tape all the walls together in the form of the roof. Cut a hole in one of the walls for the door, put the piece you cut out in the empty hole, then tape it on the inside on one side of the door. Put a thumb tack into a small piece of foamboard and put it to where the foamboard piece is holding the door shut, now to open the door just turn the foamboard. now cut a hole into the front wall for the firing slot and add some effects, poke holes in the walls to simulate gunshots, scratch to make it seem like its been attacked by orks with axes. It should look like this
here is a little teaser of is in the making