A Brush with Catacombs.

I won't be cryptic: there are bones down here.

Rome, Italy - The cool air of ancient history closed in on us as we descended 12 feet into the Earth, along narrow tunnels carved into volcanic rock during the second and third centuries.

Yes, second and third.

The Catacombs of St. Callixtus are the largest in Rome and hold the dusty bones of more than a half-million people, including 56 saints, 16 popes and a number of martyrs. I'm not religious, but that's an impressive roster for Team Halo.

As the air whispered in my ear, I almost expected a bony finger to reach out from behind one of the frescoes, and tap me on the shoulder.

As if on cue, a choir echoed over the walls.

More than 1,700 years after it was completed, a subterranean mass is still held here.