The Grotta Gigante is an enormous cave, first opened to the public in 1908, and is large enough to contain the entire basilica of Saint Peter. Renowned for its constant temperature and characteristics it has become a site of scientific experiments of world interest. The speleological society, which runs the caves, is the oldest in Europe and organises guided tours all year round. There are a series of routes, some of which were recently opened, allow you to admire the grandeur lit by spotlights from all angles. Visit also the small museum.
