Tokyo, Japan; I'd visit for a week in either time of year. I cannot even begin to imagine all the things I'd do there, but the main thing besides exploring would be to visit all the wacky shops and restaurants!
Tip: in Japan, all purchases will be exquisitely wrapped but say "gift please" and suddenly your purchase will packaged like a work of art. My $25 umbrella came with its own box and canvas sling bag to carry the box!
"Nakameguro, located on the Tokyu Toyoko Line or the Tokyo Metro Hibiya Line... Here you can stroll along the cherry blossom lined canal, flick through art books (in English!), buy vintage clothes by weight and eat organic food from Kyoto at Aoya. Potentially Tokyo's hippest suburb, Nakameguro is super popular with designers, artists, musicians and all round creative types..."