The catalogue of UK Entrances to Hell is a collection of images of strange dark entrances (usually boarded up.) There is now a Flickr group too. Remember the safety rules:
Rule 1: It may be an obvious thing to say but NEVER try to go inside an entrance to Hell.
Rule 2: Always approach an entrance on your stomach.
Rule 3: Don’t shout at the devil (not even with good news).
Rule 4: Wear rubber gloves for 3 or 4 days after your visit.
This site came up when I googled “go to hell”.