The first place to be referred to as catacombs was the system of underground tombs between the 2nd and 3rd milestones of the Appian Way in Rome, where the bodies of the apostles Peter and Paul, among others, were said to have been buried. The name of that place in Late Latin was L.L. fem. nom. pl. n. catacumbasa word of obscure origin, possibly deriving from a proper name, or else a derivation of the Latin phrasecata tumbas, "among the tombs". The word referred originally only to the Roman catacombs, but was extended by 1836 to refer to any subterranean receptacle of the dead, as in the 18th-century Paris catacombs. All Roman catacombs were located outside city walls since it was illegal to bury a dead body within the city, providing "a place…where martyrs tombs could be openly marked" and commemorative services and feasts held safely on sacred days.
France - Catacombs of Paris. Mine workings were used at end of the 18th century and had no religious purpose other than as an ossuary for storing the bones of cleared graveyards.
Catacombs, although most notable as underground passageways and cemeteries, also house many decorations. There are thousands of decorations in the centuries-old catacombs of Rome, catacombs of Paris, and other known and unknown catacombs, some of which include inscriptions, paintings, statues, ornaments, and other items placed in the graves over the years. Most of these decorations were used to identify, immortalize and show respect to the dead. Decorations in the catacombs of Rome were primarily decorated with images and words exalting Christ or depicting scenes from the Old and New Testaments of the Bible. Much of the sculpture work and art, other than engravings on the walls or tombs, has been preserved in places such as the Museum of Saint John Lateran, Christian Museum of Berlin University, and the Vatican. Three representations of Christ as Orpheus charming animals with peaceful music have been found in the catacombs of Domatilla and St. Callista. Another figure was made of gilded glass and dates back to the fourth century, featuring Jesus with the world balanced in his hand and a scroll at his feet.
Inscriptions
Although thousands of inscriptions were lost as time passed, many of those remaining indicate the social rank or job title of its inhabitants; however, most of the inscriptions simply indicate how loving a couple was, or the love of parents and such. A common and particularly interesting one found in Roman catacombs is the Ichthys, or "Monogram of Christ" which reads ΙΧΘΥΣ, standing for "Jesus Christ, Son of God, Savior".
Bacteria
In recent years unique strains of bacteria have been discovered that thrive in catacombs, inducing mineral efflorescence and decay. These include Kribbella sancticallisti, Kribbella catacumbae, and three types of non-thermophilic Rubrobacter.
