Grotta Gigante ("Giant Cave", Slovene: Briščkova jama), also known as Riesengrotte or as Grotta di Brisciachi, is a giant cave on the Italian side of the Trieste Carso, in the municipality of Sgonico. Its central cavern is 107 metres (351 ft) high, 65 metres (213 ft) wide and 130 metres (430 ft) long putting it in the 1995 Guinness Book of Records as the world's largest tourist cave.
The cave contains many large stalactites and stalagmites many of exceptional beauty. A feature of the stalagmites is their "dish-pile" appearance, formed by water dropping from up to 80 meters above and depositing calcium carbonate over a wide area.
The enormous hall is 107 meters high, 130 meters long and 65 meters large. A comfortable and steep path and a suggestive electric lighting allows a pleasant visit of about 45 minutes. The tourist can have a look at the wonderful and charming underground world represented by the caves and at the rich calcite concretions, the highest of which is no less than 12 metres high.
The exceptional characteristics, and the constant temperatures in the Giant cave during the whole year, have suggested to place two geodetic pendula, 100 meters high approximately (the longest in the world) and other scientific instruments.
The cave was first explored by Antonio Federico Lindner in 1840. In those days, the Karst behind Trieste was being searched for the underground water of the river Timavo so as to be able to plan the city's aqueduct. In 1897, it was fully mapped by Andrea Perko, in 1905, properly equipped for guided tours and in 1908, inaugurated. After World War I, ownership went to the Julian Alpine Society. Tourism only really began in 1957, when electricity was installed, unveiling new perspectives and details.
The Museum of speleology is near the cave and besides the various speleological, geological and paleontological finds it also includes some valuable archeological pieces and a poster collection of the cave. Two wide parking lots are available on the outside. Visits are scheduled in good times and with expert guides.
