| TUFA OF THE KINGS. |
| STYLE. | SPECIMEN. | DATE. |
| Polygonal | Tusculum | —— |
| Opus quadratum. First period, squared edges | { Veii | —— |
| { Gabii | —— |
| { Palatine Hill | 753 B.C. | |
| Second period, bevelled edges | { Second Wall of Rome | 746 B.C. |
| { Aventine Hill | 600 B.C. |
| { Ostia | 600 B.C. | |
| PEPERINO OF THE REPUBLIC. |
| Opus quadratum | { Tomb of Scipio | 298 B.C. |
| { Temple of Hope | 240 B.C. |
| Opus incertum | Temple of Cybele | 191 B.C. |
| Opus incertum, polygonal | Emporium | 190 B.C. |
| Opus quadratum | Tabularium | 78 B.C. |
| TRAVERTINE AND BRICK OF THE EMPIRE. |
| Opus quadratum | { Tomb of Cecilia Metella | 78 B.C. |
| { Theatre of Marcellus | 13 B.C. |
| { Arch of Dolabella | 10 A.D. |
| { Colosseum | 80 A.D. | |
| Opus reticulatum | { Muro Morto | 80 B.C. |
| { Tomb of Augustus | 10 B.C. |
| { Palatine Tiberius' House | —— |
| { Palatine Germanicus' House | —— |
| { Hadrian's Villa | —— |
| { Hadrian's Ostia | —— |
| Opus lateritium— |
| Bricks, 6 to foot | { Pantheon | Augustus. |
| { Prætorian Camp | Tiberius. |
| { Palace | Caligula. |
| Bricks, 8 to foot | Aqueduct | Nero. |
| Bricks, 7 to foot | Palace | Domitian. |
| Bricks, 6 to foot | Temple of Venus and Rome | Hadrian. |
| Bricks, 7 to foot | Nymphæum, on Palatine | M. Aurelius. |
| Bricks, 5 to foot | { Baths | Caracalla. |
| { Nymphæum | Alexander Severus. |
| { Walls of Rome | Aurelian. |
| { Thermæ | Diocletian. |
| { Basilica | Constantine. | |
| Bricks and tufa | { Circus of Maxentius | 300 A.D. |
| { House of Gregory | 590 A.D. |
| Opera Saracenesca | S. Sisto Vecchio | 1200 A.D. |
| Opus Spicatum | Herring-bone pavement. |
| Opus Signinum | Cement for reservoirs, etc. |