We asked Aicher, author of "Guide to the Aqueducts of Ancient Rome," about the Romans' sophisticated ... Tunnels don't disturb surface activities such as farming or traffic, and that's a plus.

A cross inlaid in the floor of a library marks the spot where Indiana Jones has to dig to access the ancient catacombs of ... To find catacombs, go to Rome, home of some of the oldest and longest ...