I have a soft spot for these types of projects. Much like the submerged vacuum tunnel that could connect Western Europe and the Eastern USA with trains going at 3000mph, I think we progress as a society when we challenge ourselves in such a way

This would be incredible but I must ask who here would spend 2 days on a train instead of 10 (ish) hours on a plane to get to Beijing? I also cannot imagine that the train would be price competitive should it be built. However it would be a nice way to stop at many places along the way and see a collection of cities and countries

There was a series on Discovery a while back that covered the submerged tunnel, Tokyo MegaCity (pyramidal structure housing up to 500,000 people or so) and other projects that border on the impossible. Great viewing