The dirt-filled arena is where all the newly-designed weapons are tested. Of course, they test them on dummies. All the workers viewing the test keep track of anything on the weapon in need of improvement. Hope you enjoy! It was a fun build.
Wreckage from a previous mishap. You can even see a few bits from the last test dummy.
The sign is to warn workers not to enter the danger zone. Plenty of workers have been blown to bits by going off limits when an extremely powerful cannon blasts right through the wall.