Abstract: A building has an exterior shell with exterior walls and a roof, defining an interior space. There is a fire resistant, structurally supportive core within the interior space. The core is preferably of hollow, reinforced concrete, having a door opening and a fire resistant door mounted adjacent thereto. There are support members inter-connecting the shell and the core. These may include cables connecting corners of the core to corners of the shell and connecting the roof of the shell to the roof of the core. There may also be rigid supports connecting the roof of the shell to the roof of the core.