|Photo of the Chair of Saint Peter, taken in 1867 and|
included in the Catholic Encyclopedia (1911).
The phrase "chair of Saint Peter" has both literal and figurative meanings. In the more abstract sense, The "seat" of Saint Peter is the Holy See -- the Sancta Sedes, or the episcopal jurisdiction of the Pope in Rome, symbolizing the leadership and unity of the One, Holy, Catholic and Apostolic Church. More literally, we think of the actual chair, or cathedra, upon which the Apostle Peter actually sat. While a Chair of Saint Peter in Antioch (of dubious history) exists in Venice, it is believed that the authentic Chair in Saint Peter in Rome may be found to this day at the Vatican.
As early as about AD 200, we have the testimony of Tertullian in De Praescriptione Haereticorum that pilgrims could visit the chair upon which Peter sat in Rome:
Come now, thou who willest to exercise thy curiosity to better purpose in the business of thy salvation: go through the Apostolic Churches where the very thrones of the Apostles at this very day preside over their own districts, where their own genuine letters are read which speak their words and bring the presence of each before our minds. If Achaia is nearest to thee, thou hast Corinth. If thou art not far from Macedonia, thou hast Philippi. If thou canst travel into Asia, thou hast Ephesus. Or if thou art near to Italy, thou hast Rome, where we too have an authority close at hand. What a happy Church is that whereon the Apostles poured out their whole doctrine together with their blood; where Peter suffers a passion like his Lord's, where Paul is crowned...As for the reputed chair itself, I have included an image of it along with this post (see above). The Catholic Encyclopedia (1911) gives a very detailed provenance for the cathedra which is not necessary to replicate here. A modern description is offered in Roma Sotterranea: Or, Some Account of the Roman Catacombs, Especially of the Cemetery of San Callisto (1869) by Rev. J. Spencer Northcote and Rev. W. R. Brownlow as follows:
The Chair has four solid legs composed of yellow oak, united by horizontal bars of the same material. In these legs are fixed the iron rings which make the whole a sella gestatoria such as that in which the Sovereign Pontiff is now carried on state occasions, and such as those which the Roman senators began to use in the time of Claudius. The four oak legs were evidently once square, but they are much eaten away by age and have also had pieces cut from them as relics. These time worn portions have been strengthened and rendered more ornamental by pieces of dark acacia wood which form the whole interior part of the chair, and which appear to have hardly suffered at all from the same causes which have so altered the appearance of the oak legs. The panels of the front and sides and the row of arches with the tympanum above them which forms the back are also composed of this wood. But the most remarkable circumstance about these two different kinds of material is that all the ivory ornaments which cover the front and back of the chair are attached to the acacia portions alone and never to the parts composed of oak. Thus the oak framework, with its rings, appears to be of quite a distinct antiquity from that of the acacia portions with their ivory decorations.For more, check out Roma Sotterranea on Google books. That work also contains an even more detailed history of the Chair, along with a discussion of a second cathedra of Peter existing in the Cemetery of Ostrianus.