In only one night, the Basilica was destroyed by fire.
A significant appeal was launched by Pope Leo XII to all the faithful: the Basilica had to be rebuilt in an identical way, re-using the elements preserved from the fire, in such a manner that the Christian tradition could be maintained as it had been since its origins.
Parts were moved, restored, demolished, and reconstructed. Not only did a multitude of Catholics respond to the appeal, but gifts arrived from all over the world. For example, blocks of malachite and lapis lazuli were donated by Tsar Nicholas I. These were going to be used for the construction of the two sumptuous lateral altars of the transept. King Fouad I of Egypt gave columns and windows of very fine alabaster as a gift, while the vice-king of Egypt, Mohamed Ali contributed by offering columns made of alabaster. Thus, it became the Church of Rome’s most important construction site of the 19th century.
On December 10, 1854, Pope Pius IX (1846-1876) consecrated the “new” Basilica in the presence of a great number of Cardinals and Bishops, gathered in Rome from all over the world for the proclamation of the Dogma of the Immaculate Conception.
1) Letter Ad plurimas pasque gravissimas of 25 January 1825.
2) Architects like Valadier, then Belli and afterwards Luigi Poletti directed the work until 1869.
3) A long list of all their names is engraved along the walls of the apse.