An open door leads into the unknown. 
<dl><dd>Seen in January 2018 at the construction site in front of the <a href="//commons.wikimedia.org/wiki/Bonn_Hauptbahnhof" title="Bonn Hauptbahnhof">Central Station in Bonn</a>, Germany.(station forecourt, so-called <i>Bonner Loch</i>)</dd></dl>
<a href="//commons.wikimedia.org/wiki/User:Spielvogel" title="User:Spielvogel">Spielvogel</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>