Out of curiosity, you entered into this ruined factory to have a look inside the factory. As you got inside, the door got locked and you tried your best to open the door, but everything went in vain. The final option would be to find the ways and means to lock the door. If you are fortunate, you may get the key to open the door. But, you need to solve some difficult puzzles to get the key and escape from the ruined factory. All the best!