Treasury Tunnels

One thing all the elites in the world have in common is amassing wealth - but where does it all go? The church has a very simple (yet complicated) answer for you: the treasury tunnels. No one knows how vast and complicated these are or how deep they truly go. You can find anything you want in them, but should you venture down there unnanounced (or gasp! uninvited!), you will also find your end. Sooner than later.
While every church has a basement or a catacomb system to hide what means to be hidden (like skeletons and inquisition chambers with soon-to-be-skeletons), there is one basement system that overshadows them all - the ones below the central cathedral in the Ardenian empire. The eastern wing of the cathedral is what is commonly referred to as Treasury, a place that accepts donations and tributes to the church and various other offerings. Everything is then carefuly catalogued and recorded and then sent away through a complicated system of levers and small elevators to wherever they need to go next. A single person does not know how far these tunnels reach and how many other church buildings they connect, clergymen focused on accounting are only responsible for a singular sector at a time with very little contact with the other ones. They also often take on the vows of silence so their influence over the material treasures of the church cannot be easily influenced by outsiders.
The tunnels under the treasury are rumoured to be bigger and more complex than the biggest silver mines of the empire and more and more tunnels and chambers are being carved out every day. It is a never ending and constantly evolving labyrinth that is meant to preserve at the same time as confuse would be intruders.