Note 80 — Chapter I

There are great quarries of this stone below Tivoli near the course of the ancient Anio, now Teverone. The station Bagni on the Roma-Tivoli railway is close to them. Those near the place called Barco were exploited by the ancient Romans, while Bernini derived the stone for the colonnades in front of St. Peter’s from the quarries called ‘Le Fosse,’ a little to the north of the former. Vitruvius, De Arch., II, vii, 2, writes of the ‘Tiburtina saxa’ as resisting all destructive agencies save that of fire, and the remark is repeated by Pliny, Hist. Nat., XXXVI, 22. Vasari’s account of its origin is correct. It is a deposit of lime in water, and the cavities in it are partly caused by plants, moss, etc., round which the deposit has formed itself and which of course have long ago decayed away. See O on the Frontispiece. The stone did not come into use at Rome until about the last century of the Republic, and it was not, like peperino, one of the old traditional building materials.