Cleansing Chapel

Don't farm souls here. The majority of enemies are hollows and most of the enemies outside in the graveyard are zombies who vomit maggots at you to bleed you to death. There are 6 Cathedral Knights and 2 Cathedral Evangelists, but the routes you must take to get to each one can be rather long. The zombies in the graveyard seemingly continue to spawn indefinitely after being killed. As shown in the video below, zombies won't spawn after killing a certain number of them. Clearing the graveyard can be a long and tedious endeavour, but you would earn approximately 24,418 souls.

Clearing the graveyard outside the Cleansing Chapel, Dark Souls III