As the ruins strewn about the Forum indicate, Rome had a decline ... a fabled, steep decline. That in itself is remarkable, but even more amazing was that once it hit bottom, Rome bounced. The Dark Ages were unkind to the city. As his army failed to halt the invading northerners, the last Emperor snuck out of town in 476 C.E. Rome's population plummeted from a million or so inhabitants to less than 50,000. (Some estimates say it may have dropped to as few a...

All of Rome, it seems, qualifies as an archeological site. Some of the ancient architecture was buried by Rome's frequent, sludgy floods, but astonishingly, some of the ancient buildings are still in everyday use. Much of today's city is built literally atop the sedimented-over remains of its own antiquity. Dig a bit and you may find the remains of a Roman general's villa ... or a goat herder's dung pile. Or perhaps both, for when a city has survived as long (a...