Until 1855, where the Crypt now stands there was only the solid rock from which it was dug. It was completed before the basilica: the first mass was celebrated in it on the 9th September 1861, where as the basilica was consecrated only on the 4th June 1864.
There is a great contrast between the basilica and the crypt. The one is a rather high, very ornate edifice, the other very low and bare except for a few columns. The very bareness of the spot makes a suitable surrounding for a very simple prayer.