Some places have such a resonance in the imagination that it is almost inevitable that something remarkable will occur when you visit them, even for the first time. Artist William Crozier looks back on some of his most important influences.

Padua, in Italy, had occupied such a place in my mind, but it was not until the late 1950s that I finally came to visit this semi-mythological city.

On that first trip, my only intention was to visit the Scrovegni, or Arena, Chapel, painted by Giotto around 1305. I felt very familiar with the frescoes on the basis of a small Skira monograph, with its grey-and-white reproductions, that I had owned since my teens, and I had read the exchange of letters between Giotto and Scrovegni, his patron.

In my view, Giotto was something of a hero, a superstar. Nowadays, the Scrovegni Chapel has a great website, but the result is as misleading as my 1940s Skira reproductions.

In those days the chapel was not the preciously guarded tourist attraction it is today. It was, in Jean Cocteau's great phrase, famous but unknown, and to gain entrance you had to find the caretaker's house and ask him to walk down a quarter of a mile or so, to open the door. The man had always something more urgent to do, but eventually he was persuaded.

On our walk down I realised that he was as enthusiastic about the chapel as I was, although in his case it was less excitement than veneration. In his view, Giotto had moved from divine artist to sainthood.

When he unlocked the door and threw it open, I realised that he had stretched out his arm and was barring my path. In my confusion, he asked me to look at a large stone, about eight feet by eight feet, that formed the floor in the entrance to the chapel.

He explained that this was the main entrance, laid by Scrovegni's workmen before Giotto began his cycle of frescoes. The significance of this was not apparent to me, but then the caretaker looked at the stone and, addressing it as much as me, began to intone: "Giotto's feet walked across this stone, as also did those of Massaccio, Donatello, Leonardo, Michelangelo . . ."

The list went on and on, spanning six centuries and finishing with Matisse and Picasso. It was a virtuoso performance, probably delivered with equal gravitas for every visitor who bothered to seek out the place, but I was completely overawed and intimidated. This was sacred ground.

He put his hand on my back and ushered me into the chapel. Inside, he gave me the key, asked me to return it to him and left me there alone.

I was too overcome with emotion to study Giotto, although with great trepidation I did touch one panel, The Resurrection. But the memory of that day lasted. This caretaker had taken me from one life to another, across a large stone where others in my trade had walked.