The structure Keroman III in the <a href="https://en.wikipedia.org/wiki/Keroman_Submarine_Base" class="extiw" title="en:Keroman Submarine Base">Keroman Submarine Base</a> in Lorient, France - The roof.
<a href="//commons.wikimedia.org/wiki/User:NemesisIII" title="User:NemesisIII">NemesisIII</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>