The art of exploring underground caves, tunnels, steam tunnels and other such goodness in urban areas. We used to do a little of this in DunedinNewZealand but never got really involved. I'm thinking that PortlandOregon might be a good place to go investigate places like the ShanghaiTunnels (not the bar
and such that supposedly exist round abouts.
General resources ...
Resources on specific areas ...
- New York Tunnels
- Myseteries under Moscow
Articles ...