You cannot teach here. You need to ask for a permit and that is only given a few times a year. Limited to cave divers, but only if you know the right people. 3 divers is also the max.
It is no cave, but it is overhead. In some places you can breathe some air above you. But you cannot get out. Most parts are completely overhead.
It is small. Only 10 tot 10m or so with 2 layers (highest layer is just halve of the bunker square meters). There is some line, I guess about 50m from the stairs to the round at the bottom. No lines on the bridge at the highest layer. You cannot teach here. The viz will become zero really soon. Sediment at bottom, perculation from old steel above you. Also it is narrow, more or less as narrow as you can find in wrecks. There are 3 bunkers. We dove only the first 2. The 3rd is more away from the others and is more difficult to get in. You need to climb over gates, but you are allowed if you have the permit.
Yes, this has history. It is now a free accessible parc to walk around and climb on some old things like the high blast furnice.
Hochofen 5 // Rundweg Industriegeschichte | Landschaftspark Duisburg-Nord
It shows the history of the steel industry from around 1900 till 1985 when they stopped with everything here. It is a nice place for safe urban exploration, a lot of photographers use the parc to make pictures and it has a really nice scenery.
There is also another place to dive: The Gasometer. This is a round silo filled with water (45m wide, 13m deep), full with objects to explore and open for every diver from open water and up. I have pictures from this divesite. But here only pictures of the 'Möllerbunker'.