The Porphyry Tazza of the Sala Rotonda of the Vatican
[See § 2, Of Porphyry, ante, p. 32.]
Ascanio Colonna, who was brother to the famous Vittoria Colonna the friend of Michelangelo, was one of the chief representatives of the imperial interests in Italy, in the stormy times of the first half of the sixteenth century. Charles V made him in 1520 Grand Constable of Naples. With Pope Paul III he had a bitter feud, and the Pope seized on his possessions. On the election in 1550 of Julius III, the new Pope, in order to please the Emperor, reinstated Ascanio, and it was on the occasion of this reconciliation that Colonna presented to the Pope the famous basin of porphyry of which Vasari writes. The ‘vineyard’ for which the Pope destined it was connected with the casino and villa outside the Porta del Popolo which bear the name of the Pope and where is now installed the Villa Papa Giulio Museum. The tazza in question is the superb bowl that occupies the centre of the Sala Rotonda in the Vatican Museum. It is said to have been found temp. Julius II, in the Thermae of Titus (Pistolesi, Il Vaticano Descritto, V, 206), and after remaining for a time at the papal villa it was conveyed by Clement XI to the Vatican and placed in the court of the Belvedere, now the Cortile Ottagono. Francesco de’ Ficorini (Le Vestigia e Rarità di Roma, Roma, 1744, bk. II, ch. 2, p. 15) says that in this court was the ‘gran conca di porfido,’ and another of white oriental granite, both found in the Thermae of Titus. When Clement XIV (1769–75) added the octagonal colonnade in the interior of the Cortile, the tazza was apparently no longer needed there, for soon afterwards Pius VI, who with Clement was the creator of the Museo Pio-Clementino, placed it in his newly constructed Sala Rotonda, where it remains. Pasquale Massi in his Indicazione antiquaria del Ponteficio Museo Pio-Clementino, 1792, p. 118, speaks of ‘una vastissima tazza di porfido di palmi 62 di circonferenza tutta massiccia (all of one piece), la quale si trovava già in Vaticano trasportatavi dalla Villa di Giulio III, fuori di Porta del Popolo, ed ora squisitamente risarcita.’ This restoration was completed in 1792 and was no doubt carried out by the same artists whom Pius VI employed for the repair of the porphyry sarcophagi noticed ante, p. 27. In this way the work, which Vasari says in the text had to be left unfinished, was finally accomplished. Cancellieri (Lettera... intorno la maravigliosa Tazza di Porfido, etc., Roma, 1822) makes the surprising statement that at one time the tazza had been mended with pieces of white granite!
The tazza is the largest existing piece of the kind and measures 14 ft. in diameter. It is shallow and has in the interior the usual projecting central boss. Independently of this boss the tazza has only one arris, or in Vasari’s words ‘canto vivo,’ at A in the rough sketch, Fig. 9. A smaller but more artistically wrought porphyry tazza, beautifully restored, and measuring 8 ft. 6 in. in diameter, is in the Pitti at Florence close to the entrance to the passage to the Uffizi. It was a gift from Clement VII to the Medici, and was brought from Rome (Villa Medici) to Florence in 1790, where it was repaired in the Tuscan manufactory of mosaics (Zobi, Notizie Storiche sull’ Origine e Progressi dei Lavori di Commesso in Pietre Dure, Firenze, 1853, p. 118). Both these pieces are superb works, and display the magnificent qualities of the red Egyptian porphyry to full advantage.
The original purpose of these great basins is not very clear. The ‘conche’ mentioned in the footnote to p. 27, ante, though now used as sarcophagi, were certainly in their origin baths, but the shallow tazza would be unsuitable for such a purpose, and moreover the central ornament would have almost precluded such a use. There seems no sign of a central opening through which a water pipe could have been introduced, so that the tazza might serve as the basin of a fountain. Perhaps their employment was simply ornamental.