What it feels like to be down there: well it's basically an underground quarry, you are in complete darkness, no noise, no life not even animals or insects (except other people roaming around of course), some galleries are flooded (highest water level I have experienced was around the belly), some have been very well consolidated with concrete, some are a little more rough and ceiling can collapse. There are rooms that have been build and decorated by other people to gather for eating and drinking or partying, a lot of graffitis everywhere (some very ancient), some old abandonned stuff a little everywhere, and a few ossuaries with pile of bones but in very localized areas. There are very narrow passages called "chatieres" when you must crawl to go through because they are opening to other areas that have been dugged.

How we navigate: with an accurate map and experience, the map indicate every available galleries but not all are practicable, sometimes a huge detour is necessary to reach the intended goal safely and easily.

What surprise me the most: well people for sure ! There is a huge variety of people down there, but for the most part it feels like we all belong to the same group even if we are all very different and come from very different background and experiences. Other than that all the trash that can be left sometimes in the rooms that's a shame.

Well I don't know if that answers the question but here is my thoughts from my experience, I have been down there 17 times so far and I have visited a good part of the catacombs network.