The <a href="https://en.wikipedia.org/wiki/Open_hearth_furnace" class="extiw" title="en:Open hearth furnace">Siemens-Martin-Oven</a> in <a href="https://en.wikipedia.org/wiki/Brandenburg/Havel" class="extiw" title="en:Brandenburg/Havel">Brandenburg/Havel</a>, Germany. The oven is nowadays a part of Brandenburg's Museum of Industry.
<a href="//commons.wikimedia.org/wiki/User:Clemensfranz" title="User:Clemensfranz">Clemens Sterz</a>
CC BY 2.5
<span class="int-own-work">Self-photographed</span>