Usually when people picture an igloo, they imagine a dome with a little tunnel attached. This is surprisingly accurate! Igloos are surprisingly hospitable, and it all comes down to science.
Snow makes a surprisingly good insulator. When combined with ice to make the walls of the dome sturdy, it creates a cozy little environment. With the occupant’s body heat and perhaps the use of oil lamps or candles, the walls of the igloo melt a little, but then are soon frozen by the temperatures outside. Several days of this melting and refreezing process creates a nice insulation, sometimes of up to 60 degrees Fahrenheit, which is incredibly welcome when the weather outside is -50 degrees Fahrenheit!