In the older districts there is a countless variety of narrow gloomy streets, many of them steep. The houses are mostly five or six storeys high, are covered with stucco made of a kind of pozzolana which hardens by exposure, and have large balconies and flat roofs.
In the part of Herculaneum already excavated the corridors in the upper portions of the theatre are compactly filled, up to the head of the arches, with pozzolana and pumice transformed into tufa (which proves that the formation of this stone may take place in a comparatively short time).
In 1866 primitive structures were discovered in the island of Therasia by quarrymen extracting pozzolana for the Suez Canal works; and when this discovery was followed up in 1870, on the neighbouring Santorin (Thera), by representatives of the French School at Athens, much pottery of a class now known immedi ately to precede the typical late Aegean ware, and many stone and metal objects, were found and dated by the geologist Fouque, somewhat arbitrarily, to 2000 B.C., by consideration of the superincumbent eruptive stratum.
It exported iron from Elba, mosaics, pottery, manufactured locally with earth from Ischia (which was in considerable demand until 1883), sulphur (which indeed was extracted in the neighbourhood until the 18th century), probably alum (which is still worked), perfumes, pozzolana earth (taking its name from the place), cretaceous earth for mixing with grain (alica) from the Leucogaean hills, glass cups engraved with views of Puteoli, mineral dyes (the blue invented.
Lava is much used for paving-stones in the neighborhood of volcanic districts, where pozzolana (for cement) and pumice stone are also important.