Blue Grotto, Biševo

On the east side of Biševo, a small island off Vis in the outer Dalmatian archipelago, a sea cave lights up blue for about an hour around midday. The effect depends on a second, submerged opening on the south side of the cave: sunlight enters underwater, bounces off the pale floor and fills the chamber with turquoise light, while anything in the water — an oar, a hand, a stone bar crossing between the walls just below the surface — seems to glow silver. The best time is usually between 11 a.m. and noon, and the sea has to be calm. It is one of the best-known natural sights on the Croatian Adriatic and the counterpart of the Blue Grotto on Capri, which works the same way.

The cave is small, which is part of its charm. Wave action carved it from the limestone of Biševo, in a cove called Balun. It is about 24 metres long, up to 15 metres high, with water 10–12 metres deep. For most of its history the only way in was to dive. Baron Eugen von Ransonet described and painted it in the 19th century, and on his suggestion a passage wide enough for a small rowing boat was cut in 1884 — 1.5 metres high and 2.5 metres wide. Visitors still go in that way today, in a small rowing boat.

The number of visitors has grown far beyond what the entrance can take at once — more than ten thousand a year even by older counts — so queues form outside. The visit is run by the Komiža Nautical Centre, which publishes the current queue and sea conditions online. Boat trips often also stop at the nearby Green Cave, a larger cave coloured emerald by a similar effect.

Getting there

The cave is about 4.5 nautical miles (roughly 8 km) by boat from Komiža on Vis, where excursions start. Split, about 68 km away as the crow flies, is the gateway: Jadrolinija's car ferry to Vis takes about 2 hours 20 minutes, and the catamaran via Hvar about 1 hour 30 minutes. The nearest airport is Split (SPU), about 66 km away.