Often equipped only with head lamps and homemade maps, they explore the tunnels and ancient rooms, sometimes staying underground for days at a time.

CNN: Loving life in Paris' Empire of the Dead

Finally, housed in ancient, arched basement tunnels, is the Museo Archeologico containing a vast collection of pieces found near Siena, including elaborate Etruscan alabaster funerary urns and gold Roman coins.

BBC: Two days in Siena, Italy