Wow. Interesting. My dreams sometimes are similar and also involve underground tunnels and stuff like that.
Often there are also pools of water, sometimes those tunnels or underground chambers look like parts of a canalization, sometimes it looks more like a cavern with stalactites hanging from the ceiling. I'm never alone in those caverns, there is something lurking there. Often zombies or alligators, following me or trying to eat me.
Sometimes I find an exit out of the cavern and it leads into a different setting, maybe a forest. When I'm in a forest I often have bow and arrows with me and feel like I'm hunting for something.
It may also be an old city, full of little streets with timbered houses, a huge cathedral and a castle. There's a train station there and often I'm dreaming of taking the train or riding the bus around this city. Sometimes I'm walking through a deserted shopping mall there, searching for someone I was supposed to meet. Then I return to a parking deck to search for my car. Sometimes I end up driving around with my car, never reaching my destination.
Another setting which is quite frequent in my dreams is a hotel. In those kind of dreams various people I know are involved. But often I'm supposed to save them from some danger.
And of course I'm dreaming of my house with additional rooms and hallways, staircases, attics and cellars. Sometimes full of stuff, like globes, harps, pianos, all covered in dust. Once I had this dream of a small door appearing in one corner of my room and it lead to one of these rooms that were full of things, but something was waiting for me there, I knew and I didn't want to enter the room. To lead over to the real scary nightmares I can remember: I was looking out of the kitchen window into the garden and there was a man walking around, with a black tail coat and a top hat and an unrecognizable face. Just walking around in the garden and sometimes looking up. I was so scared he would try to enter the house.
Another nightmare was about two children who were sitting in my living room, one was blindfolded, the other gagged. There was another girl standing in the room, who kept screaming and was swallowing nails and fixing pins. And I desperately tried to make her stop, but it didn't work.
I can try to think of more. My dreams are often very vivid and I can remember a lot of them.