Ruins describes the pre-Cataclysm structures of all types still existing on Celestia. This includes a wide selection of buildings, both above and below ground. However the below ground structures outnumber the remaining above ground structures several times over. For the most part the modern peoples of Celestia cannot tell one type of facility from another, though some do seem to be mines complexes and these are the only types roughly understood by modern people. Many specialized creatures exist within ruins that appear nowhere else on Celestia and modern people have many ideas for why this is.