On: Massive triumphal marble arch built by Romans to honour Emperor Titus discovered

[jahnu]

Could they not just go deep enough to avoid all that?

[danmaz74 → jahnu]

That's something I often wondered about, but I'm pretty sure there will be some reasons why it's not feasible... I also think that the biggest problems are the stations.

[din-9 → jahnu]

Subway lines need stations, ventilation and often big shafts to build the tunnels from.

[jccooper → jahnu]

The lines are deep enough, with tunnelling, to avoid historical layers; mainly it's the stations that end up with archaeology.