1. The Word Means "House": In the Inuktitut language spoken by the Inuit people, the word iglu simply means "house" or "home"—and it can refer to any kind of home, not just ones built from snow!

2. Snow Acts Like a Blanket: Even though snow is cold to touch, packed snow is full of tiny trapped air pockets. These air pockets trap your body heat inside, keeping the room surprisingly warm compared to the freezing wind outside.

3. It Can Be 60 Degrees Warmer Inside: When it's a freezing -40°F (-40°C) outside, human body heat alone can warm the inside of an igloo up to 20°F to 60°F (-7°C to 16°C).

4. They Are Built in a Spiral: Igloo builders don't stack snow blocks in flat circles like bricks. They carve the blocks so they slope inward, stacking them in a continuous upward spiral that locks the dome together without falling.

5. The Doorway Is Lower Than the Floor: The entrance tunnel to an igloo is usually dug slightly lower than the living area floor. Because cold air sinks and warm air rises, this "cold trap" keeps the chilly drafts from getting into the sleeping area.

6. Fire Makes the Walls Stronger: When people use small lamps or body heat inside, the inner layer of snow melts slightly. When it refreezes, it turns into a smooth, solid sheet of ice that turns the igloo into an extra-sturdy shelter.

7. Built Made-to-Order in Under an Hour: Experienced Inuit builders can harvest hard snow blocks and construct a complete, sturdy shelter in just 30 to 60 minutes.