One of the big construction trends in Tokyo has been putting train lines underground. Given the space crunch here, I can see how it makes sense. I think most of the land will be given over to construction and not green space. While I can understand the economic impetus, I really think it heightens a feeling of detachment from one's community and decreases the aesthetic value of a place.
Granted, the trains can be crowded, uncomfortable and sometimes smelly. But some of the best lighting I have ever seen has come through a train window and illuminates a person in just the right way that they seem to glow or take on the appearance of a sublime portrait. The time frame of this lighting is pretty limited, usually a couple hours in the morning and a few in the afternoon and not so much when it rains. Still, it's enough to give someone a moment to pause and go "wow."
A common complaint from people who ride subways is that they feel like a mole. They travel underground and pop up to ground level at various exits. These people often lament that they couldn't find their way from one station to the next if they had to walk on the street --even though some of the stations are only a kilometer apart. It's hard to feel how your area connects together when you have a patchwork of experiences to piece together.
This mole-like experience limits one's experience to a smaller area around the station. If you don't really know what's around, why bother leaving the station area? It's a natural reaction if one has neither the time nor inclination to explore. A number of times, I decided to visit some places to take pictures, some shops to buy bread or have a cup of coffee based on something I have seen from a train window. Sometimes these places are good, but just as often, there's a better place just a little bit out of view from the station exit.
In a way, more than people being hooked into their phones, portable games or internet, I think that this transition to underground transportation is going making the urban living experience more sterile and detached.