The wife and I spent a quiet day at Tokyo Metropolitan Government Building, or Tokyo City Hall. The Observatory is famous for the views on a clear day and also for being free. I even overheard an Asian American guy commenting that he read about this building in one of those "Free Things to Do in Tokyo" articles.
The day was a little cloudy so we didn't get to see Mount Fuji from there. We did however find the Tokyo Prefecture tourism office and got ourselves some brochures for things to do here.
Strange, this kind of tourism help would have been useful at the airport instead of at this government building. We found the staff helpful and spoke to us in good English.
We still had presents to buy for the kids so it was off to Akihabara Electric Town. I wanted to show the wife what the place looked like. We mainly checked out the toy and hobby stores, since my missus was not into the gadgets.
I think she was sufficiently impressed. She has never seen so much Japanese pop culture in one place.
I kept her away from the adult section of some of the book stores we went to though. I think she'd be a little taken aback at some of the manga sold there.