A couple friends and I for some reason decided to go to one of those mines where you can go like “1.5 million years into the past” via a massive mine shaft in a super futuristic 45 degree elevator; it was fully enclosed but the entire front was thick two inch glass and the thing descending at a stupefying speed, like 60 mph or something. It looked like a subway except you were going down, flourescent lights flashing by you. Obviously you lost cell service and all you could hear was the machinery, your breathing and the occasional crackle of the intercom.
At one point the elevator stopped, moved horizontally, and continued; you could see traces of lava that the main shaft had been overtaken by. That is about the time that the forced air kicked in and we realized we were breathing recycled air. Also around this time is when we started the “whose idea was this? this was a stupid idea, you are stupid, we are dumb, why did we agree to this, we are going to die in a tourist attraction.” comments.
Once at the bottom the intercom clicked on and the attendant explained the process; there were mining shacks and what was basically a self serviced hotel down there you could stay at for up to a week provided you brought your own supplies. The old mining tunnels had been reinforced with titanium/adamantium (yup) and you could walk around looking at old rock exhibits. Plaques explained the history and composition of what you were looking at, including the machines that had been used to mine whatever was being mined.
I woke up not long after but just the feeling of that descent down that elevator at such a speed, into the bowels of the Earth was fucking awesome.
tl;dr, lucid dreamed I went down a 60mph horizontal elevator into the Earth 1.5 million years into the past