If you are in Tokyo I recommend to follow this path.
Get out at Kudanshita station, exit 2 and walk all the road down to Jimboucho to find tons and tons of old books. Even if you don’t understand Japanese, it’s very interesting to see the atmosphere in there. Then you’ll find streets dedicated to sports, then streets of music and finally you will be in Akihabara, the geek kingdom.
View Books, Sports, Music, Electronics in a larger map