A station box is a term in the construction industry: It describes a box-like underground structure for a transportation system, for example a metro or tube station. Station boxes are built in two methods – "top-down" or "bottom-up". In the "bottom-up" method, a chamber as large as the station structure is dug into the ground into which the station is built. Poured concrete or pre-cast panels are then used to form the various levels and internal structures, similar to the construction of the underground basements of high rise buildings. When the construction is complete, this station box is covered again up to the street level.