My seven-year-old recently fell in love with planets so we made the journey to Cosmo Planetarium in Shibuya. We tried to walk there from a main walking street, but just couldn't figure it out, and eventually took a taxi. The building is actually a huge community center type of complex with different activities, with the planetarium on the top floor. The planetarium itself is all in Japanese - so if that bothers you, then don't bother. But wow, for about five u.s. dollars, and even less for kids, you enjoy a full hour of a show. the facilities are fairly small which make it quaint. we actually saw one of the more academic offerings which was kind of boring. however, they have four or five different shows every day and i think the other options are a bit more entertaining. We enjoyed getting away from the hustle and bustle of shibuya to chill in this place for a while. staff are very nice and accommodating, but again, essentially no English to be found - so figure out how to function once you get inside but it really shouldn't be a problem if you're patient. this isn't exactly a 'must do' in shibuya, but if you need to pass some time and have done everything else in shibuya, it's definitely worth a visit.