I had a very similar experience. I used to do a lot of "urban exploring" in the UK, and as part of that, I visited Paris for it with some friends. We went with a guide I met on a forum to a secret resistance shelter recently uncovered at the time, and there was still litter from the 1940s. Old cigarette and match boxes, wine bottles, old posters and the like. It was exactly as you describe; intimate, in the way that visiting a mausoleum or cathedral is compared to a museum. I'm sure it's been picked clean now, but the memory will stick with me forever I suspect.