What Happened to the Roman’s Streets and Buildings?

Descend down to the Milan subway train.

Then, to one side is a glass window.   You peer through it and look at some blocks.   A little sign says that these are the street blocks that the city’s people built in the days of the Roman Empire.  Wow.  How did that street get buried so deep? If it’s true that it takes 300 years to form 1 inch of soil, why does this seem to happen so much faster in cities?   Is it all the dust and waste that people make that accelerates the soil formation that covers up the cities?

The magnificenDuomo Cathedral in Milan now stands at the center of radiating streets in Milan, Italy.