Strange recurring dream/nightmare I've had for years

It's hard to pinpoint but I've had this dream since maybe 10 years ago. It occurs rarely, but I always recognize it.

It's dark outside, I'm on a large plain of sorts, next to me there's sometimes a building like a church, but it could be just a house. In front of me is a rectangular hole in the ground and a staircase leading down like a set of basement stairs. Descending the stairs, I will see that the ground/ plain was like a ceiling above a vast darkness, that's criss-crossed by staircases that lead up and down, left and right like a maze. I will descend the stairs for a bit but eventually something ominous will rise from below and I will run back up until I'm outside again on the plain. I never see what's approaching me but it feels dangerous, I immediately know I'll have to run back.

What could this mean?