Feel the glow: under the mountain into a radon spa in Austria

Bad Gastein’s curious attractions include tunnels where visitors can soak up low doses of natural radiation, which is claimed to help cure eczema and other ailments

The Austrian Alps are known for their visually dramatic walking trails. But equally alluring are the sumptuous spa-hotels where hikers can relax aching limbs in a maze of saunas and steam rooms, all scented with eucalyptus. And no spa is more labyrinthine than the radioactive caves I found myself (naked) in in Bad Gastein.

This elegant spa town was built on a rocky perch beside a spectacular waterfall in the declining years of the Austro-Hungarian empire: in the late 19th and early 20th centuries, belle époque hotels were tapping the radon-rich thermal waters to offer curative stays to bourgeois visitors.