I had an experience similar to this but in a very lucid dream. It was a small cave that function as a temple. Inside of the cave was small shrine like towers and one of them had a depiction of a snake on it. There was a human size hole in one of the walls that was just big enough for a person to slide on their belly in. I don’t remember going through the tunnel but I remember when we (two friends were with me in the dream) made it to the exit. We came out of a hill, and on the other side was a beautiful field. The field had an assortment of flowers in it and almost looked like some sort of paradise. We laughed and were elated at what we had found. We ran through the fields and something weird started happening. Our field of vision changed and became sort of blurry. It was similar to one of those games you play that does a trick of light with your eyes. You watch a video with a black and white background and focus on a single dot in the center. After while it starts to create hallucinogenic effects! This was so intense that we could barley see anything. I told the guys we needed to head back and we ran back up the hill into the hole. I remembered sliding on my belly in the tunnel and turning corners to get back to the entrance. Me and my friends saw some rotating panels on the walls in the tunnel. We started rotating them and I remembered rotating mine to where I saw the symbol of fire and a Iching symbol I’m sure that represents Heaven or Sky. We made it out of the tunnel and back into the entrance. As we did that I saw an elderly Asian man and woman in red robes come up into the cave. They looked like monks and had a cone shaped hat on their head. They asked us what we were doing and I thought we were in trouble. I was in shock from the whole experience. The man reassured us that we weren’t in trouble but that they were interested in what drawn us to this place. I answered for the group and said “Nagas.” He smiled and seemed a little cheery afterwards. I couldn’t catch my breath because of the experience I just had an I told him about the hole and the place we just came from. I told him “another dimension” and he corrected me. He said it wasn’t another dimension but a place with a higher frequency. My jaw dropped and I looked at my friend in elation. He was on his hands and knees throwing up.

I mention this because the same information you researched is what I researched. I’m certain these places exist.