Blast door for radioprotection. The metro station Pankstraße was designed to be used as a public fallout shelter. Both entrances to the entresol can be sealed with one of these concrete sliding panels. The only way into the shelter would lead through the airlock which is marked by the red arrow.
<a href="https://de.wikipedia.org/wiki/Benutzer:Ren%C3%A9_Kr%C3%BCger" class="extiw" title="de:Benutzer:René Krüger">René Krüger</a>
2011-09-16
German Wikipedia