A site I read, BBSpot.com, had a link to:

http://www.japantimes.co.jp/cgi-bin/getarticle.pl5?fl20030301a1.htm

This is an article about Shun Akiba and his book "Teito Tokyo
Kakusareta Chikamono Himitsu" ("Imperial City Tokyo: Secret of a
Hidden Underground Network"). By comparing old and new maps of
Tokyo, he apparently discovered "7 riddles", most or all involving
the Toyko subway system.

It's completely off-topic, but when I saw it I immediately thought of
the old DCMetroCrawlers. Check it out - maybe you will too. The
article is in English.

*sr*