When I was a kid, we lived towards the bottom of a hill on a curve with our neighbors with kids our age directly across the street. The curve was such that when the plow came around, most of the snow was deposited on the neighbor's side of the street. They had a colonial split-rail type of fence along the street and the snow bank piled higher than the fence in a good storm. One very snowy snow-day, a bunch of us neighborhood kids learned that the fence actually provided a decent support for a snow tunnel. We each dug our own forts into the snow bank through the horizontal planks of the fence, and had an epic snowball fight.

Then we realized it was much more fun to connect each of our forts so we could actually talk to each other (at least to our adjacent neighbors). We left archways between compartments to designate boundaries of our "properties". The happy accident, I think, was the arches provided better support for the whole structure. There were 4 or 5 of us, each with our own room that we could sit up in and just about lay down in head to foot inside our own spaces, and also crawl in between. Once our parents realized what we were up to, and always thinking about safety, they made us wall up any entrances on the streetside so that we could only crawl in from the safety of the neighbor's yard. It was the '70s.

The tunnel survived nearly the entire Winter and as time went on, our breath condensed on the inside and iced up the walls and floors. And we poured water on the outside to ice up the outside walls to make them "stronger". We also found that we could enter the room at the top of the hill and slide down the tunnel on our bellies all the way to the end. This was paradise for a kid!

As Winter wore on, parents issued additional rules, like no playing in the tunnel when it was snowing due to the possibility of a snow plow coming by and collapsing the tunnel. And no climbing on top. But that tunnel never collapsed and remained structurally sound until probably late February / early March. That was probably the most magical Winter of my childhood.