How old?

Beside our hotel in Sorrento is a huge crack in the earth from an earthquake 20,000 years ago. 

In the crack, below street level, is a drain and an abandoned 5 story building.  (I took the pic at street level)

Steve asked how old the building was.  I couldn't see a sign anywhere so I took a punt and said 'well maybe they abandoned it 50 years ago looking at the foliage'. 

What the hell would I know. It turned out to be a Roman flour mill that is over 1500 years old! 

As we say a lot these days, 'holy crapola'...