Grotta Gigante
This record was broken in 2010 when La Verna cave in the south west of France was opened to tourists, measuring 255 by 225 by 195 metres (837 by 738 by 640 ft).A feature of the stalagmites is their "dish-pile" appearance, formed by water dropping from up to 80 m (260 ft) above and depositing calcium carbonate over a wide area.A steep path with atmospheric electric lighting allows the visitor to spend about 45 minutes in this underground space, with its rich calcite concretions, the highest of which is no less than 12 m (39 ft) high.Its available space and the constant temperatures throughout the year have led to the placement of scientific instruments, including the two Grotta Gigante horizontal pendulums which hang down from about 100 m (330 ft), and are the longest geodetic pendula in the world.In 1897, it was fully mapped by Andrea Perko, properly equipped for guided tours in 1905 by Club Touristi Triestini, and inaugurated in 1908.