On 15 July 1823 a fire, started through the negligence of a workman who was repairing the lead of the roof, resulted in the almost total destruction of the basilica which, alone of all the churches of Rome, had preserved its primitive character for 1435 years. It was re-opened in 1840, and reconsecrated 1855 with the presence of Pope Pius IX and fifty cardinals. Completing the works of reconstruction took longer, however, and many countries made their contributions. The Viceroy of Egypt sent pillars of alabaster, the Emperor of Russia the precious malachite and lapis lazuli of the tabernacle. The work on the principal facade, looking toward the Tiber, was completed by the Italian Government, which declared the church a national monument." (Text from Wikipedia).