I was staying with my son before the New Year.
I dreamt that we were walking down a corridor which then became a tall and wide underground tunnel, cut out from sandstone, but with an earthy floor. It was brightly lit, but had no lights. After a while, I was reading a book, and he told me that we were in a police library, and thinking that I was trespassing, I went back out into the corridor, which shortly became a gently curving tunnel again. There may have been some junctions, but the only one I remember was an arch about a foot tall on the right. I was just able to crawl through it (I found it easier to go backwards), and through it was another spacious tunnel - but I was worried about the possibility of getting trapped in there, and returned to the previous tunnel.
Shortly after this, I had a large pro video camera on my shoulder, which was connected to a team of people at my starting point by an apparently unlimited unreeling cable. As I went along the tunnel (bending to the left at this point) I suddenly lost contact with the video team - but when I stepped back, it was restored. Holding a loop of the cable in front of me also made the signal go. I realised that if I proceeded, I would be in an alternate or parallel universe, and might not be able to return, so I turned round and went back to my starting point, winding up the cable. When I reached the waiting team, I found that the signal I was getting through the cable - both ends of which were now in view - was different from what was being said in front of me. After some strange misunderstandings, I understood that I was now in a different universe, but my cable was still connecting me to the original.
Then I woke up, and took a while to get back to sleep, as I was confused as to what universe I was in.