tomb, vault or chamber constructed either partly or entirely above ground as a place of interment. Although it is often used as a synonym for grave, the word is derived from the Greek tymbos [burial ground]. It may also designate a memorial shrine erected above a grave. The concept of the tomb as a chamber or dwelling place for the dead is the most widespread. It may have originated in the practice, known in prehistoric times and common among so-called primitive peoples of today, of burying the dead underneath their place of dwelling. Sometimes the survivors continue to live in the house; sometimes they seal and abandon it after a burial. This may account for the recurrence in different periods and places of the domed or conical funeral mounds and chambers (such as the prehistoric barrow, the beehive tomb of Mycenaean civilization, the mausoleum of Persian and Roman royalty, and the stupa of Asia) and of the artificial caves commonly called rock-cut tombs (such as those found in Petra, Jordan; Thebes, Egypt; and in various parts of Asia). When corpses were buried outside the house, the purpose of protecting the body and possibly confining the spirit was often served by heaping stones above the grave. This may have been the initial structure that gave rise to the mastaba and later to the pyramid of Egypt. Such heaps of stones also served as markers or shrines where offerings might be left to the spirits of the dead. Christian tombs, relatively simple at first, had by the Middle Ages become quite splendid. It became the custom to build a church over the grave of a martyr. For centuries, kings and other privileged persons were buried within the church buildings, their graves often surmounted by a little shrine or by a sarcophagus bearing an effigy of the deceased. In Great Britain many important personages have been entombed in Westminster Abbey. Famous funerary structures of modern times include the Taj Mahal, at Agra, India; the Dôme des Invalides, Paris, which contains the tomb of Napoleon; General Grant's tomb, New York City; and the Lenin mausoleum, Moscow. See burial; cemetery; crypt; funeral customs.