One of the four great basilicas of Rome, and an abbey nullius. Though originating as early as A.D. 200 the basilica was not completed till 395. It was destroyed by fire in 1823; the whole world contributed to its restoration which was completed in 1854. In 1891 the stained glass in the basilica was shattered by an explosion. Pope Martin V entrusted the monastery to the monks of the Congregation of Monte Cassino in 1425. It was then made an abbey nullius