Grottes de Baume The Jura Mountains

The 30-million-year-old Grottes de Baume are secreted away in the cliffs 2km south of Baume-les-Messieurs. On guided tours, visitors can weave their way along 2.5km of passageways, with stalactites dangling above and limestone crags looming from the shadows. Allow an hour for the tour, bring a sweater, and listen out for the flutter of resident bats. If you plan on visiting the Abbaye Impériale too, note that a combined ticket costs €13/6 per adult/child.