We rented a backdrop (Times Square) and then had two painted flats which we brought on and off which folded in half and were free-standing - the convex sides were the sewers and the concave sides folded out to be the mission. The flats were 6'x6' with a fold in the middle, so they were made up of two 3' wide panels hinged together. The Hot Box we did with a rear curtain and fabric.