One of the old chestnuts in D&D is that dwarfs have a special ability to sense sloping passages that humans would be fooled by. On a long enough sloping passage, humans could blithely go down a level without noticing. The problem with this one is that it has always taken away an ability that normal humans have in real life. It is not hard to sense whether you are walking uphill or downhill on a street or in a corridor with very little slope to it. It would have to be a very shallow slope indeed to not be noticeable unless D&D humans and elves and halflings are very thick indeed when it comes to sensing slopes. And even if they cannot feel it, it takes the simple device of a marble or a small pair of wheels on an axle or a dribble of water onto the floor and see which way it goes unless the floor is irregular enough to conceal slope or mucky enough or channeled or otherwise impedes mechanical slope detection. A plumb line and plumb square is another way to pick out slope conveniently and will give an answer even if the floor is a mess, if you can see far enough, though that is often not the case in dungeons.
So for the dwarf slope sense to really matter compared to a human, you'll need to make the floor irregular enough to be confusing and disrupt taking a level mechanically or invoke the mythic underground which has properties of confusing human senses regarding slopes but a dwarf can see through the subterfuge.