Topsoil is the top, or surface part, of the Earth. This is where Topsoilers live, and where the Tunnels series first starts. Topsoil consists of the seven continents and the oceans. Although Topsoil is a very advanced place, most of its residents do not know about the underground world beneath it. The Colonists and Styx have had a hate for Topsoil for centuries and wanted to reclaim it.