Cosmo Planetarium Shibuya

Conveniently located and good for kids and adults alike

Of the numerous planetariums in the Tokyo area, Cosmo Planetarium is a great option for its convenient location. They have a range of different programs, from ones geared to kids (typically only shown on weekends, at least at the moment) and other ones more suitable for adults. The programs shown are only in Japanese, so it's important to keep that in mind, but I do think even if you don't have a great grasp on Japanese that it's still very enjoyable. Admission prices are very reasonable too -- especially compared to what I'd pay for a similar venue back home.