<p>The <p><span style="text-decoration: line-through;">The question may be a bit confusing because you are writing about the Trade Quarter, and the map points to the Facotry Quarter. Quarter</span>. Anyway, you go through this door shown on the map when doing the Shadows of Yalahar Quest. The mission related to this door is called "Out of the blue".</p><p>Source: <a rel="nofollow" href="https://tibiopedia.pl/quests/Shadows_of_Yalahar_Quest">https://tibiopedia.pl/quests/Shadows_of_Yalahar_Quest</a></p>