The Aventine Hill keyhole with the view of St Peter’s Basilica is no longer a secret – the permanent line of tourists is proof that it’s been well and truly discovered. But there’s another view of St Peter’s, a little off the beaten track, which hardly anyone knows about.

My boyfriend brought me to Via Piccolomini on the back of his scooter one evening, promising to show me an optical illusion. As we sped through the sleepy backstreets of a residential neighbourhood near Villa Doria Pamphili, I wasn’t sure what to expect. But then we turned a corner, and there it was – the dome of St Peter’s, rising up like the moon at the end of the street. We drove towards it, but the closer we got, the further away it seemed. This is the magic of Via Piccolomini – the shrinking dome.

The optical illusion works on foot too, but the illusion is much more striking when you’re moving fast. Rent a scooter or car to experience the Eternal City’s best-kept secret.