There is one Winkelturm in Stuttgart Feuerbach, that is sometimes open for visitors. Here is a link in German http://www.schutzbauten-stuttgart.de/de-de/f%C3%BChrungen/%C...

When these bunker were built in Germany in the 1930's new designs has to be tested to get approval. Does the test site still exists? This would show various designs.

More pictures of an interior and cross section here: https://www.abandonedspaces.com/uncategorized/bunker-town.ht...

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