The steel mill X was described to me as huge and abandoned. Perfect ingredients.

True, but that wasn't the whole story. Part of this huge steel producing monster is in the process of being destroyed while the rest is a working factory. Therefore whole the place is guarded and it isn't simple to nose about unnoticed.

Entering through a hole in the fence opposite the working factory is straightforward.
An open window invites you in an administrative building with workshops.

Now comes the hard part : the workshops are separated from the blast furnaces by approximately one kilometer of open wasteland. It's a game of chance whether or not you stay unnoticed.

Run straight across like a rabbit ?
or hop from shelter to shelter scanning for guards ?
simply walk the distance, acting as director of engineering, showing that any interference on your inspection round won't be tolerated ?

I chose the last option but I doubt if my army boots, stained clothes and photo equipment would have convinced anyone ...