Caving tours under Trieste's Carso Plateau

The Grotta Gigante's name is no joke for this giant cave is big enough to fit Rome's St Peter's basilica inside. The largest tourist cave in the world, the Grotta Gigante is over 100 metres high, 260 metres long and 65 metres wide and it can be found in Sgonico near the capital of Italy's Friuli-Venezia Giulia region, Trieste.

Inside, large stalactites and stalagmites form an underground world rich in calcite concretions for caving enthusiasts. Artistic lighting offers unusual perspectives and highlights important detail to simply enjoy the cave itself.
The cave's unique properties and constant temperature mean it is used as a scientific station, with a horizontal pendulum that measures seismic and tidal events. But it's also used for more dreamy motivations and is available for weddings and social events.

The Trieste plateau, also known as the Carso, which borders Slovenia in Italy's north-east, is a plentiful trousseau of around 1500 caves and caverns in various types, sizes and depths. They are fantastically decorated with all their underground accessories.
The Trebiciano cave is another example, 350 metres deep and opening onto the underground section of the Timavo River. The river starts in neighbouring Slovenia, runs underground across the border and re-emerges in springs near Duino.

It was the search for the Timavo River, to use as a water supply for the town, that led to the discovery of Trieste's caving wealth. But it wasn't until electricity was installed in the major caves that tourism began to flow.
The whole region of Friuli-Venezia-Giulia has 24 caving, or speleological groups, and 10 are along this stretch of the Trieste plateau. Outside the Grotta Gigante's central cavern is also a museum that presents the speleological, geological and paleontological elements of the caves along with their valuable archaeological finds.