| Built of uniformly gray, granular volcanic tufa, or peperino, the courtyard was completed by 1579, as recorded in the building documents. |
| Among the 30 different types of stone recognized are varieties of diorite, granite, bedded tuff, sandstones, limestones, and tufa. |
| Most of the churches and palaces and houses of Orvieto were also built of tufa. |
| It's an otherworldly site, fringed with dunes and studded with bone-white calcium carbonate spires called tufa towers. |
| It is perched on a plateau of tufa rock, almost like it's been carved straight from its roots. |
| Along the shoreline, pinnacles of calcium carbonate deposits, called tufa, glare white in the sunlight. |
