Capri’s single most famous attraction is the Grotta Azzurra, a stunning sea cave illuminated by an other-worldly blue light. The easiest way to visit is to take a tour from Marina Grande; tickets include the return boat trip but the rowing boat into the cave and admission are paid separately. Allow a good hour.

The grotto had long been known to local fishermen when it was rediscovered by two Germans – writer Augustus Kopisch and painter Ernst Fries – in 1826. Subsequent research, however, revealed that Emperor Tiberius had built a quay in the cave around AD 30, complete with a nymphaeum (shrine to the water nymph). Remarkably, you can still see the carved Roman landing stage towards the rear of the cave.

Measuring 54m by 30m and rising to a height of 15m, the grotto is said to have sunk by up to 20m in prehistoric times, blocking every opening except the 1.3m-high entrance. And this is the key to the magical blue light. Sunlight enters through a small underwater aperture and is refracted through the water; this, combined with the reflection of the light off the white sandy seafloor, produces the vivid blue effect to which the cave owes its name.

The grotto is closed if the sea is too choppy and swimming in it is forbidden, although you can swim outside the entrance – get a bus to Grotta Azzurra, take the stairs down to the right and dive off the small concrete platform. When visiting, keep in mind that the singing ‘captains’ are included in the price, so don’t feel any obligation if they push for a tip.