It makes you wonder what else is buried beneath the streets of cities built on top of ancient ruins. Cairo, Alexandria, Rome, Mexico City, Athens. Cool stuff, if you ask me.
Early cathedrals in Ireland incorporate pieces of pagan buildings: https://goo.gl/images/a5cduy
Rome has one of the most underdeveloped subways among major capitals, simply because digging anything is very difficult: as the article mentions, soil is quite peculiar over there, and technically it's a city built over several hills. Add the archeological element, and you might as well give up.
Crikey, I have heard countless stories from farmers, old construction workers and so on of coming across burial sites, ancient tools or dinosaur bones, where they have just covered the stuff up, buried it further down another hole or even destroyed it just because they had no care or knowledge of that stuff.
Some of the stories are pretty interesting (like caves with paintings of mega-fauna or sites of ancient fish farming), but some are also horrifying (One old bloke found a giant bone on his property while clearing scrub, he burnt it).
One of my grand-uncles told me that when he was a kid (early 20th century) when they found ancient vases they used them for sling practice, it was only later that people realized they had any value.