§ 12 Of Travertine
There is another sort of stone called travertine, which is much used for building and also for carvings of various sorts. It is always being quarried in many places throughout Italy, as in the neighbourhood of Lucca, at Pisa, and round about Siena; but the largest blocks and the best, that is, those which are most easily worked, are taken from above the river Teverone at Tivoli.80 The stone is all a kind of coagulation of earth and of water, which by its hardness and coldness congeals and petrifies not only earth, but stumps and branches and leaves of trees. On account of the water that remains within the stones—which never can be dry so long as they lie under water—they are full of pores which give them a spongy and perforated appearance, both within and without.
Of travertine the ancients constructed their most wonderful buildings, for example, the Colosseum, and the Treasury by the church of Ss. Cosimo e Damiano81 and many other edifices. They used it without stint for the foundations of their public buildings, and in working these basements, they were not too fastidious in finishing them carefully, but left them rough, as in rustic work; and this they did perhaps because so treated they possess a certain grandeur and nobility of their own.82 But in our days there has been found one who has worked travertine most skilfully, as was formerly seen in that round temple, begun but never finished, save only the basement, on the piazza of San Luigi de’ Francesi in Rome.83 It was undertaken by a Frenchman named Maestro Gian, who studied the art of carving in Rome and became so proficient, that his work in the beginning of this temple could stand comparison with the best things, either ancient or modern, ever seen carved in travertine. He carved astrological globes, salamanders in the fire, royal emblems, devices of open books showing the leaves, and carefully finished trophies and masks. These, in their own place, bear witness to the excellence and quality of the stone which, although it is coarse, can be worked as freely as marble. It possesses a charm of its own, owing to the spongy appearance produced by the little cavities which cover the surface and look so well. This unfinished temple being left imperfect, was razed by the French, and the said stones and other pieces that formed part of its construction were placed in the façade of the church of San Luigi84 and in some of its chapels, where they are well arranged, and produce a beautiful effect.
Travertine is excellent for walls, because after it is built up in squared courses and worked into mouldings, it can be entirely covered with stucco85 and thereafter be impressed with any designs in relief that are desired, just as the ancients did in the public entrances to the Colosseum86 and in many other places; and as Antonio da San Gallo has done in the present day in the hall of the Pope’s palace, in front of the chapel,87 where he has faced the travertine with stucco bearing many excellent devices. More than any other master however has Michelagnolo Buonarroti ennobled this stone in the decoration of the court of the Casa Farnese.88 With marvellous judgement he has used it for windows, masks, brackets, and many other such fancies; all these are worked as marble is worked and no other similar ornament can be seen to excel this in beauty. And if these things are rare, more wonderful than all is the great cornice on the front façade of the same palace, than which nothing more magnificent or more beautiful can be sought for. Michelagnolo has also employed travertine for certain large chapels on the outside of the building of St. Peter’s, and in the interior, for the cornice that runs all round the tribune; so finished is this cornice that not one of the joints can be perceived, everyone therefore can well understand with what advantage to the work we employ this kind of stone. But that which surpasses every other marvel is the construction in this stone of the vault of one of the three tribunes in St. Peter’s; the pieces composing it are joined in such a manner that not only is the building well tied together with various sorts of bonds, but looked at from the ground it appears made out of a single piece.89