Cavers crawl along with the complex illuminated by the eerie light from a head torch. The system was once reached through trap doors in Jewish villages,some of which are now archaeological sites, others have been completely destroyed. Today, they may be no more than an indistinct, shoulder-width opening in the ground or hillside. The intrepid may have to crawl, even slither for a few minutes through a pitch-black burrow too cramped for a fully armed Roman legionary. Turns can be so tight cavers may have to back up to a spot where they can flip from head to feet first...