Okay kiddo, have you ever seen a house with a roof made out of bricks or tiles? Well, in some places people make houses a little differently, using something called a Nubian Vault.
A Nubian Vault looks a bit like a house made of mud bricks, but the roof is special. The roof is made from layers of mud and sticks, put together in a special way that makes a curved shape.
This curve helps air to flow and keeps the house cool in hot places, like in Africa where the Nubian Vault was first made a long time ago.
People still use Nubian Vaults today because they are cheap to make with just mud and sticks, and they keep the house cool in hot places. Plus, it's also really cool to say you live in a vault!