Rome has its catacombs; Paris its sewers, and Seattle in America's Washington State has its underground city.So, here I am beneath Seattle's sidewalks, surrounded by a tangle of water and sewerage pipes and rubble walking through what remains of Seattle's 19th century downtown waterfront area.

I look through a window at a blank wall – a window which once looked out on a seaport town that had its origins in logging and fishing.

Seattle's waterfront, at the base of steeply rising hills, was then a muddy swamp, so low that twice a day when the tide came in the sewerage system would back up and toilets became fountains.

A person could get blown out of a toilet or drown in a pothole. A whole generation of Seattle children was raised on the tide timetable which was published daily in the local newspaper.

Visitors to town, unaware of the eccentricities of the sewerage system, often were treated to a chilling experience. Newcomers became known as "wet backs".

Read More about Seattle's underground city from Stuff.co.nz