Inverted <b>N</b> letter at the top of the ridge turret cupola of the pavillon Lesdiguières of the palais du Louvre. Perhaps the work of a worker who disliked Napoléon III.
<a href="//commons.wikimedia.org/wiki/User:Tangopaso" title="User:Tangopaso">Tangopaso</a>
<span class="int-own-work">Self-photographed</span>