What is building 400?

Without any specific context or location, it is impossible to provide a specific answer about building 400. However, here are some general possibilities:

• Building 400 could refer to a specific building in a particular area. For example, it could be a government building, an office complex, an apartment building, or a hospital. The building could be known by its address or by a name.
• Building 400 could be a code or labeling system used in a complex or campus. For instance, it could indicate a particular section or wing of a larger building.
• Building 400 could be a construction project or plan. For example, it could be a new building that is being designed or built. The project could have a specific purpose, such as a school or research facility.
• Building 400 could be a historical or architectural landmark. For instance, it could be an old building that has been preserved or restored. The building could have a unique design or cultural significance.