As catacomb, yes, they do not exist. But before being used as catacomb (to keep the remains of the dead because the surface cemeteries were full), they were initially stone quarries, starting to be used as early as the 12th century. So if you play around 1228, they are full active.
You can imagine some sections already decommissioned as they have been mined out, possibly abandoned or repurposed to store cheese, wines, possibly hosting vagrants and criminals.
Paris catacombs (or in our case stone carries) are very different from Rome's. Rome's were from the beginning (existing already a few centuries AD) used as catacomb for Christian to be able to practice their faith without incurring wrath from the authorities, until Christian faith became dominant and they would not need to hide anymore. They had to be discreet and their tunnel are one or two men-wide.
Paris' are quarries before being repurposed as catacomb: huge caves, wide tunnels are a lot more common.
These networks of quarries will be dig up to three layers deeps, so it is really a multi-level dungeon.
1 Like
Quarries? Where workers cut stone for building?
Just that. Of course, originally they were located outside the city. Then the city grew...
In Crete, of course, there's the palace of Minos, and the attached labyrinth. There could be others in other ancient cities, with either a Magic or Faerie regio.
You could look at the winding caverns of the Pyrenees as a massive dungeon.
1 Like
Cave of Twisting Shadows anyone? 
Corrected the misspelling. Yes, quarries.
If one cares about such things, it won't exist for another few hundred years if it's a 1220 saga.
OTOH, that doesn't stop the Criamon.