> It's surprising that they're not doing that systematically around the building, but then again I guess that applies to a large part of the city as well.

In some places in Italy, Greece, Malta, probably others I don't know, people always joke that you shouldn't try to ever do any renovations lest you end up finding something and lose your house. Some places you're almost guaranteed to find stuff if you just dig once or twice.

There is a wonderful museum it the Italian city of Lecce that started when someone went to fix some plumbing in their house and ended up finding so much amazing historical stuff that they ended up opening the house as a museum:

https://www.museofaggiano.it/en/home/

And that's just one house in one city in one country!

Edit: I strongly recommend the museum, Lecce and indeed all of Puglia!