In the spirit of Halloween, here's a wonderful series that features the exploration of the unknown. Photographer Steve Duncan has been exploring the underground for years. Whether it's from sewers, subways, or tunnels, everything is fair game. Check out a few of his pictures he's taken along the way. As a bonus, we've also included a video of his journey.
Check out more about his work and what he does at his website:
[Via Wall To Watch]