How far down is Paris Metro?

Answer 1

a) Most of the métro is just underground; it was built by opening up the street, taking out a trench just taller than the tunnel, and replacing the street over the top.

b) In places, the metro tunnels under hills. It goes deepest under the Buttes Chaumont (32 metres) and the Butte Montmartre, where Abbesses is the deepest station at 36 metres.

c) Several lines have open-air sections, and some of these are elevated 10 metres above the roadway. There are also two double-decker bridges, on which the metro is high avbove the river.