Think I got it off QI ages ago, and told a work colleague today when we were talking about roads in cities, he told me I was talking rubbish.

I was under the impression that the city streets/ roads basically grew in height over time, due to the constant application of manure etc. and chippings to cover it. To the point where ground floors of buildings were no longer ground floors over a century or so of this process, as the road/street essentially grew? Thus explaining those weird windows that face the ground of pavements in big UK cities etc.

Is there any way of validating this, I've scoured the internet to no avail :(