Journalist Matthew O'Brien has been visiting the flood tunnels underneath the desert city for 12 years, getting to know its inhabitants and publishing two books on the inhabitants of the city's drains.
On his first expedition, he carried a tape recorder, a flashlight, and a baton for personal protection. Now, he knows the residents by name and counts some of them as friends.
In a recent partnership with Seeker Stories, he brought a video team to take a look inside the world.
It's a remarkable insight into the hidden world underneath the casinos and bright lights, where resourceful residents scavenge from the city above them - roulette tables become hanging curtains, shipping pallets are repurposed as beds, and cold surfaces act as refrigerators.
"I wouldn't want to be homeless anywhere else," said Craig, one of the residents of the tunnels, as long-term residents develop luxuries in their camp, from coolers to couches.
Yet as O'Brien points out, these are still flood channels - and they can rapidly fill with water during heavy rain.
Ricky, a poet who scrawls quotations from Paradise Lost on the walls, says he knows he has no future, and is well-suited to tunnel life.
"I'm past 50 years old, [with] an extensive prison background," he said, saying he'd stay underground for life "unless you can think of a better future than I can."
O'Brien established the Shine the Light community group in Vegas, which provides counselling and services to the people living in the drains.
He is also the author of Beneath the Neon, a book charting his first trips into the underworld.