He was born in Rome, near the Campo Marzio. De Rossi was a friend of Giuseppe Marchi, Superintendent of the Sacred Relics and the Cemeteries. Marchi had establised the method of studying archaeological finds on site, rather than moving them and thus losing sight of their context. This was a great leap forward in archaeology, and de Rossi adopted the principle. He was a prodigy, having copied Greek manuscripts at the Vatican Library from the age of 14.
As a loyal member of the Catholic Church, he was asked by Pope Pius IX to publish his works under the Vatican imprint. This did not prevent him from studying and publishing his finds objectively, and he was accused of being an 'ally of the Protestants' in 1856. Fortunately, the Pope did not take these accusations seriously.
His first major project, which he started working on in 1842, was to assemble and publish all known ancient Christian inscriptions in Rome. It took him 15 years to do this, and in 1857 the Vatican press printed his Inscriptiones christianae Urbis Romae. The work contained 1126 inscriptions dating from the year AD 71 to 589
While working on Inscriptiones, de Rossi also explored the catacombs. He built on Antionio Bosio's research, and made extensive use of the old Itineraries, pilgrim guides to the catacombs. The first catacomb he explored, in 1848, was that of Praetextus.
His most famous discovery was made in 1849. It was known from older sources that there was a papal cemetery in one of the catacombs, and it was though that it was located close to the Cemetery of Callixtus on the Appian Way. In a shed belonging to a wineyard, he found a stone with the partial inscription ...NELIUS MARTYR. The only possible name was Cornelius. Pope Cornelius (251-253) died in exile, and was therefore considered a martyr. De Rossi continued his search of the area, and found the Chapel of the Popes in the Catacombe di San Callisto, where 14 popes were buried. He also excavated the catacomb of Thrason (1872) and of Catacomba di Priscilla (1880's).
In 1863 de Rossi founded the Bollettino di archaeologia cristiana to publish his finds. The next year, he published the first volume of Roma Sotteranea (Subterrenean Rome); vols. 2 and 3 were published in 1867 and 1877. While doing the research for this historical work, he was assisted by his brother Michele.
His publications in the Bollettino were translated to French, and he inspired other archaeologists to study early Christian cemeteries throughout Italy.
- ↑ A later edition of Inscriptiones contained a total of 1374 inscriptions. The first four were scrapped as forgeries, meaning that the oldest known Christian inscription in Rome is a memorial to Emperor Caracalla's chamberlain Prosenes, who died in 217.