Graffitied service cover, Surry Hills, Sydney, April 2010

I sometimes like to think of the pavement as a roof – the roof of the busy underground world that supports our day-to-day living. And if the pavement is a roof, then manholes (correct term:  maintenance holes) are skylights, and service covers are the shutters on those skylights. I wrote earlier about how I tried to peer down a chink in one of these ‘shutters’ to see the Paris sewer system below. How gauche can a tourist get?

Geoff Manaugh makes a good suggestion on his BLDGBLG site: how about installing ‘upside-down periscopes’? In vertically dense cities, he proposes, these would allow everyone to peer down into subterranean infrastructure, exploring subways, cellars, plague pits, crypts, sewers, buried rivers and streams. They would be a kind of archaeological ‘truth window’.