This is an old tunnel a few hundred meters from where we live.  In the first 50 meters a lot of water comes in through the roof.  In the winter there are often a lot of ice “stalagmites” but this year the formations are really spectacular. To be honest seeing all this took my breath away.
I was really lucky on two fronts. The first was that I decided to look into the tunnel at all, which involved wading through a few meters of deep snow. The second point of luck was that the sun was very low in the sky and shining directly into the tunnel, lighting the formations in this special way. 
There are nine more images on my flickr site including some closeups.