Here are some absolutely spectacular photographs of sewers, drains and tunnels, taken by urban spelunkers from London, Bristol, Manchester and beyond:
[Images: See this ridiculously great website for loads more photographs – almost every one of which could be uploaded onto BLDGBLOG with open enthusiasm – as well as for relevant bits of info on tunnel locations and all further et ceteras; meanwhile, an upcoming BLDGBLOG entry will pursue more of this, with a London bias, soon].
An entrance to the topological undercity, a parallel world of drains and bricked abstract passages, monolithic concrete feeder chutes re-leading lost rivers through darkness.