PREAMBLE

I know of a charming grotto on the northern face of Capri, an island some small distance from Naples in Southern Italy. It is accessible only to swimmers and the tiniest paddle-boats through a cleft in the rock-face. It is obscured from sight, positioned at the base of a thirty foot cliff, hidden by the foam of wave crests, and without beaches or promontories close by from which to overlook.

From dawn to dusk boats sweep past the entrance, clockwise around the island to Sorrento, counter-clockwise to Amalfi and further out across the gulf to Palermo, to Corsica and Cagliari. The routes are carved into the face of the erratic waters, torrid and placid by turns,  roughly incised throughout numberless centuries by numberless hulls, many of which drowned and came to rest at the rocky bed of that gulf. And of this vast and motley flotilla – the corsair galleons, the fishermen, the submarines and the ferries – most aboard will have sailed past the grotto quite unaware of its existence, although nowadays it is better known.

The demigods of sea and wind have ravaged Capri. Its waterline, like some hideous ribbon around a parcel, is freckled with pores of which the grotto is just one. Through time the island’s sleek, moon-coloured façade became disfigured, and the rock itself was hollowed out with winding veins and cavities: an old rosewood timber, outwardly impeccable, ridden with weevil grubs. Some of these hollows are empty, and whistle in the wind. Some are clogged with earth and the deep roots of myrtle and cypress trees, such that the island’s haunch is awash with lush, subtropical greenery. Other patches of the island, those facing windward, are by contrast quite barren, battered by salt and spume.

And so in amongst the wilderness, organic and lifeless, manmade and god-made, to spy out that particular grotto to which I refer is to find a needle in a haystack, or a certain brick in a great wall. To find it requires purpose and patience and a good map, or, as I had on my first visit, a knowing guide.

The closest mainland port of convenience is Sorrento, an hour’s drive from Naples, and there, at a price, you will find an armada of pleasure-boats at your disposal, manned by cheery, boisterous, and for the most part disreputable sailors. The distance from Sorrento’s marina to the grotto, depending on the route taken and the condition of the sea, is between ten and twelve nautical miles (or thirty, should you travel from Naples itself). Two hours later, or half that under steam, you will arrive at the island’s north face, and a quite shallow inlet where larger keeled boats must drop anchor at once. The rest of the journey to the grotto can be swum, or rowed in a dinghy. The partly submerged ingression, at the foot of a sheer cliff, is perhaps eight feet at its widest and much less in a swell. In stormy weather, which is rarely forewarned, you must time your entry so as not to be dashed to a pulp against the roof of the cave. And beware also the coral teeth along the sides, which given the opportunity will flay you into slithers.

A short tunnel, approximately twenty feet in length, opens into a vast chamber and the rocky floor falls away beneath you, out of sight. The temperature of the water falls with it.

Glancing behind, the entryway to the grotto forms a neat triangle, like a white pupil in the heavy black iris of the cave’s interior. The crests of waves sweep into that fissure, one after another, plugging the gap momentarily and blotting out the sun. But the grotto stays lit somehow, brightly enough to discern a companion’s features, for instance, or details on the wall of the cave. The seawater itself is the medium for this unnerving glow, and through a simple quirk of architecture. There is a second notch in the rock-face, somewhat larger than and several feet beneath the first, also leading inside the grotto. It is fully submerged at all times, though not so deep down that questing eel-like sunbeams cannot reach it through the swell.

And in certain hours of the day, when the sea and sky are aligned just so, these coiling, sinuous rays penetrate the interior through that second notch, and illuminate the cavern from beneath. From the white sandy floor, up through the cold, pulsating current comes an eerie light: neon blue, pale and soft.