Or is a stalactite that has broken off from the ceiling.
I certainly don't know as I am sure it has been that way for a long time.
You can see from this photo how the lighting was difficult in the cavern.
It was either too harsh or not enough light.
There were no tripods allowed so you kind of had to just shoot and go.
I found the sports setting worked best to handle the light.
My kit lens doesn't have a very low aperture so I let the camera pick the settings.