[tjpaudio]

Oh come on now, really? I have a piece of farmland in the middle of nowhere and let me tell you, even digging a hole out there is harder now than it was 100 years ago because of the things you find buried. Subways in 200+ year old cities? I can't even imagine. What do you do when your borer, designed for medium size rock and dirt runs into a 4ft wide brick and cement wall the city forgot about 40 years ago? This happens! Also, back 100 years ago we were talking brick, cement, some steel, and thats it. Today there is a vast array of engineered materials and machinery that didn't exist back then. It's not 1,000s of unskilled workers with shovels anymore, its hundreds with technology and mostly engineers.

[Someone]

The problem in old cities isn’t as much that they can’t get through old stuff, but more that they don’t want to because of archeology.

For an example, see the Bosphorus tunnel in Istanbul (https://www.theguardian.com/world/2006/jan/25/turkey.iantray..., https://en.wikipedia.org/wiki/Marmaray#Delays)

A huge find, unfortunately on the location where a terminal was planned.

[xyzzyz]

Unskilled workers can dig through rock and concrete just fine, you just give them power tools. We don’t use them anymore not because they aren’t suitable tool for the job, but rather because they got more expensive per hour worked in the meantime, by a factor of 10-20x.