Shibuya might not look like the most child-friendly destination with it's infamous crowds and noisy streets, but National Children's Castle or Kodomo no Shiro will make you reconsider.
Children of all ages will find something to do there. Babies and toddlers can enjoy rolling around and climbing on the soft blocks in a space just dedicated to them. Older children can burn some energy in the indoor playground offering plenty of climbing, sliding, balancing and swinging opportunties. For budding artists or kids who just like to get messy with glue and paint, there is an arts and craft studio where parents can assist younger children, or older children can create masterpieces on their own. There is a music room with instruments the children can try, a computer room with activities for the kids, a corner for older children in 4th grade and above to hang out with entertainment like pool tables for their use, a video library with over 20,000 titles, a gym (call to see the schedule of sports), a roof garden with little bikes the kids can ride on and a roof top pool open in the summer months, while in the basement there is another pool open year round for preschool age children to adults (small fee applies). There are several areas for eating (you can bring your own) and plenty of drink vending machines. There is a nursing room, restroom facilities including child-size toilets, and a lot of diaper changing stations. Finally there are child care and development classes (Japanese) and a Well Child Clinic where your child can get a health check up, though this is available by appointment only.
The National Children's Castle is closed on Mondays except if Monday happens to be a national holiday, in which case it will be closed the following day.
The cost is 500 yen for adults, 400 yen for children aged 3 - 17 and free for younger children. The ticket is for the entire day so if you decide to go out for lunch and return later, just make sure to keep it. If you live in the area or plan to visit a lot, it is recommended you buy a Weekday Pass which costs 3,000 yen and entitles you to visit on weekdays for period of one year from the date of ticket purchase. Unfortunately it is only available for adults. There is also a good value Summer Pass for children and adults. If you sign up for the Tomo no Kai membership you'll receive 10 free admission tickets and monthly newsletters (Japanese). Generally the National Children's Castle is open from 10:00am - 5:00pm on weekends, national holidays, and during summer, and 12:30pm - 5:00pm otherwise. You can check the schedule on the site.
The National Children's Castle can be accessed from either Shibuya station or Omotesando station. There is parking in the building but spaces are limited and the cost is quite steep at 300 yen for 30 minutes.
Address: 5-53-1 Jingumae, Shibuya-ku, Tokyo 150-0001