of small crystal pyramids are preserved in the treasury of the basilica. The pyramidal shape seems to be an homage to pyramidal tombs in the chapel. Materials The use of rare and expensive stones all over the chapel is an important characteristic invoking the interior of the Pantheon which was the main source of inspiration for Raphael. He was very much aware that the ancients used more precious materials than contemporary Renaissance architects and intended follow their example. In a letter to Pope Leo X (c. 1519) he wrote: "...even though these days architecture may be very clever and very closely based on the style of the ancients, [...] nevertheless the ornamentation is not done using raw materials of similar expense to those used by the ancients, who, it seems, realized what they envisaged with endless amounts of money and whose will alone surmounted every difficulty." As a painter Raphael was naturally attracted to the vivid colours of the different kinds of stones available in Rome since the antiquity, and his patron, Agostino Chigi was one of the few people rich enough to finance a project that aimed to recreate the largely lost chromatic exuberance of ancient architecture. At the time of Raphael the coloured revetment of the Chigi Chapel was a complete novelty in Rome, and it remained exceptional until the Cappella Gregoriana in St. Peter's Basilica was decorated in 1578-80, but during the Baroque era the use of coloured marbles became very common. White Carrara marble (with grey veins): fluted pilasters; white "bianco purissimo" Carrara marble: capitals and friezes; statuario marble: altar steps; white and grey bardiglio marble: pavement; Egyptian "rosso di Syene" granite: monolith entrance step; africano and rosso antico marble: frames of the niches; rosso di Numidia: shells of the niches; Portasanta marble: pyramids, balusters; verde antico: bases of the pyramids; giallo antico: mouldings of the bases of the pyramids, balustrade; rosso di Numidia and Portasanta rectangles, africano borders: revetment behind the pyramids; arches, entablement and moulding rings of the dome: white Carrara marble; rosso antico: frieze above the tombs. In popular culture Part of Dan Brown's book Angels & Demons takes place in the Chigi Chapel, where the sculpture of Habakkuk and the Angel is one of the four "markers" leading to the Illuminati's secret lair. Gallery Notes Bibliography Marcia B. Hall, Rome (Artistic Centers of the Italian Renaissance), Cambridge University Press, 2005 Antonio Muñoz,