Dear Xavier,
I highly recommend Kyoto even though it is a city, because it is surrounded by beautiful mountains, and has many different temples and shrines. If you go to the Gion section you may be able to see some Geisha or Maiko. There are also many universities in Kyoto so there are much more young people than you would expect for the old capital of Japan.
There are also some beautiful nature things to see close to Kyoto. To the west, there is Arashiyama where the autumn leaves are really beautiful. To the east is Lake Biwa, the largest lake in Japan. To the south is Nara, the ancient capital of Japan. To the far north, there is Amanohashidate which is one of the 3 most beautiful places in Japan.
Cheers,
David in San Francisco