exploide
I'm relatively sure that this is not a silo but a bunker. This Commons picture is already referenced in the tagging: https://commons.wikimedia.org/wiki/File:Darmstadt_Carl-Schenck-Ring_Winkelbunker.jpg
And this should be kind of a thing that this German Wikipedia article describes: https://de.wikipedia.org/wiki/Hochbunker

However I don't think it commemorates anything, so according to the Wiki, I changed it to historic=building.