This article is under construction. Please excuse the mess.
In the hierarchy of all trains--or is it perhaps capitalized, I do not recall--there is one engine that storms ahead of the others. "The Burning God Among Iron Trains" is its name, but the Disciples of the Triadic Pyre call it simply Fire Alight. Well, whatever you might call it, it's a damned big one. And it needs to cross the Ojan like anything else. And thus: The Bridge Cathedral. Largest structure of its kind in Sangfielle or anywhere. At two miles across, it's partly a church, partly grim city, and partly an engineering pit. What are they engineering? Well... It turns out, being the devotees of the Fire Alight shifts your relationship with other trains. At least the ones who, themselves, are under the Burning God's thrall.
Bridge Cathedral is a landmark that is both a bridge and a cathedral. A two-mile-long railway bridge crosses the Ojan; as the trains crossing here includes their god, the Disciples of the Triadic Pyre built a grand structure there, part house of worship and part engineering pit.
The Jade Moon stopped at Bridge Cathedral at the end of Episode 32. According to its itinerary, the Deacon of the Blood was to board, with some time also for passengers to visit local destinations. And boy, did they.
In "Six Travelers: Pickman" the Bridge Cathedral was said to have "a big hole in the side of it," possibly due to the Fire Alight.