But what makes this visit to Rome memorable in his life and in literary history is that it was the occasion and date of the first conception of his great work.

"It was at Rome, on the 15th October, 1764, as I sat musing amid the ruins of the Capitol, while the barefooted friars were singing vespers in the temple of Jupiter, that the idea of writing the decline and fall of the city first started to my mind." The scene, the contrast of the old religion and the new, the priests of Christ replacing the flamens of Jupiter, the evensong of Catholic Rome swelling like a dirge over the prostrate Pagan Rome might well concentrate in one grand luminous idea the manifold but unconnected thoughts with which his mind had so long been teeming.

Gibbon had found his work, which was destined to fill the remainder of his life.
Henceforth there is a fixed centre around which his thoughts and musings cluster spontaneously.

Difficulties and interruptions are not wanting.

The plan then formed is not taken in hand at once; on the contrary, it is contemplated at "an awful distance"; but it led him on like a star guiding his steps, till he reached his appointed goal.
After crossing the Alps on his homeward journey, Gibbon had had some thoughts of visiting the southern provinces of France.