it was there for the Drone, or perhaps for the two Civil engineers to find should they pay enough attention to their surroundings.
It was set inside concrete wall, between a crumbling tunnel and a support pillar, the soft patina of rust covered the metal door that was roughly ten feet tall by five feet wide. The concrete didn't seem to match the aged brick of the surrounding structure either, if found, there was no discernible markings, as rust and corrosion from the damp dark environment hid any markings on the hatch.