> You could not build anything like them in modern day. You can not build it in the USA. London is about to open the newly built Elizabeth line, which cuts thr

> You could not build anything like them in modern day. You can not build it in the USA. London is about to open the newly built Elizabeth line, which cuts through the city with 60 miles of tunnels. Modern Metro/Subway infrastructure can be built in densely populated areas like Chicago and NYC. It's a political issue, not an engineering one.