The best-known snow shelter is the igloo. A brilliant use of engineering and resources, this simple dome made out of snow blocks is both strong and versatile.
Arctic cultures such as the Eskimo and the Inuit developed it, and over time they came up with a hundred tricks to make the shelter more comfortable and sturdy, including making the entrance small (to help keep heat in) and melting the inside of the dome and letting it refreeze (for increased strength).
BUILDING AN IGLOO
Diameter: Not to exceed 10 feet. Anything bigger would require a perfect dome, which is next to impossible to construct in the field.
Materials: Top layers of dry powder won’t work. Pack mounds of snow until they harden, or cut blocks of snow from the depth where your feet stop sinking.
Entrance: Build a door in the ground, about 18 inches lower than the ground inside the igloo, and tunnel below the wall into the igloo. For proper ventilation, never seal or close the entrance.
Walls: Cut the blocks into a spiral layer, leaning one block against the next. Keep the interior wall smooth so moisture can run down the side of the wall, instead of dripping from the ceiling. Include a vent hole to allow for better circulation.