Igloo

Igloos are Generated Structures that were added in Update 1.0. They can be found in cold and snowy Biomes.

Exterior
Igloos are constructed of mainly Snow Blocks, with three Blocks of Ice on each of the structure's sides, excluding the entrance.

Interior
All Igloos contain a Bed, Redstone Torch, Crafting Table, Furnace, and 12 White Carpets (or sometimes Light Grey Carpets). However, some Igloos can also generate with "Basements" which contain a trapped Villager, Zombie Villager, a Brewing Stand, some Red Carpets and a Chest with loot.

Loot from the basement includes a Golden Apple and the Brewing Stand has a Splash Potion of Weakness which can be used to cure the Zombie Villager, which gives the Player  the _Zombie Doctor_ Achievement. The basement can be accessed by a Trapdoor hidden under a carpet.

Trivia

 * Igloos are the second naturally generated structure to spawn with Zombie Villagers inside.
 * The other such structure is an Abandoned Village.
 * Igloos contain Redstone Torches because regular Torches would cause the Ice to melt.
 * Igloos are very useful if a world does not contain any Villages as the Zombie Villager can be cured and bred with the other Villager.