>>717498814
Anon those corridors are in fact part of the dungeon. The entire game map besides the end points of the branches in the second half (besides Crystal Caves), and the DLC exist in a fully traversable set of intentionally designed pathways filled with various connections, secrets, and variable difficulty depending of what "level" of the dungeon your on, just with both vertical and horizontal traversal.
Demons Souls is 4 Dungeons
Dark Souls is a Megadungeon
Dark Souls 2 is 4 Dungeons
Bloodborne is mostly another Megadungeon
Dark Souls 3 is a mainly Linear Adventure with the Cathedral, and the Irythil Dungeons/Profaned Capital as dungeons.
ER is a handful of well designed Legacy Dungeons and a thousand Micro-Dungeons but got better with it in the DLC