An air structure or air supported structure, commonly referred to as "domes" or "bubbles", are a low cost alternative to other building types typically used to provide protection from the elements for anything from private tennis court to a large sports stadium. The air structures are based on maintaining air pressure within a fabric envelope slightly higher than exterior air pressure. The larger "dome" structures have a fabric roof anchored to exterior walls where smaller ones have fabric anchored to a concrete lip set in the ground.