Underneath its glitzy casinos, far from the bright marquees, there is another Las Vegas, a pitch-black, dank underworld virtually unknown and unseen by those who live, work and play above.

About 300 people _ mostly men battling demons of various addictions _ live in the underground storm system built to protect the desert playground from the infrequent cloudburst.

There's no sign or word of welcome down here. Drug use is nearly universal. Most people carry makeshift weapons and the police don't often come unless they're called.

But the denizens have found a haven in the labyrinth of concrete tunnels that snake beneath the city and its suburbs.

In a place where total darkness can be just one bend away, visitors to this urban netherworld stumble across the unexplainable. A beat-up teddy bear lies next to a dirty chef's knife propped up against a wall. Graffiti turns into murals near sparse pockets of light.

A scruffy black cat's meow is startling as it scrambles in a pile of junk to escape a flashlight's beam. The echoes of footsteps change as boots hit standing water, or accidentally kick empty beer bottles as they tiptoe past midday sleepers. Fetid smells of garbage, dirty water and wet cloth waft through the corridors.

Each subterranean encampment can be as spartan as a few worn blankets, or as elaborate as an apartment fitted with queen-size beds, dining utensils and knickknacks.

One camp just west of the Las Vegas Strip is wallpapered with hardcore pornography, a collage of magazine pages modified with hand-drawn comic book-like dialogue bubbles giving voice to naked women.

"You'd be surprised the things that wash down in this channel ... it's hard to even describe," said Rick "Iron" Cobble, a 45-year-old Oklahoma native, who sleeps in a 5-foot-high tunnel near the south end of the glittering Strip, not far from the "Welcome to Fabulous Las Vegas" sign.

Cobble, battling severe drug addiction while living near a mound of washed up garbage, said his only belongings are a small mound of blankets and his clothes.

"Right now I'm just trying to survive," Cobble said. "That's the only way you can put it."

Rich Penksa, a retired correctional sergeant who began traversing the tunnels earlier this year for a nonprofit's homeless outreach, said he first heard about the tunnels years ago from prison inmates who told tales of living under Sin City when not behind bars.