Update 2018 : this building has been torn down, so now it's just sand and a volleyball net next to the canal! Nothing unique at all as I thought an indoor sand box was such a great idea, now it's dead.
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This is SO needed from November through April and then on rainy days during the spring and summer! It's right next to the canal so walk all the way down and you'll find the entrance which reads as "Pub McCardell" as the entrance leads to a cafe/bar next to the outside terasse. Once you walk through the cafe, you'll see a giant gym filled with sand. Perfect for volleyball and other sand sports.
I went for the 10am-12pm Sunday morning kids play. It's $6 per child and they don't charge for adults. There are toys, balls, frisbees there so no need to bring your own.
What's not to love about this and for the price it can't be beat! I can imagine how awesome it gets to sit on the terrasse in the summer. They also have live music certain nights.
I also enjoyed the music.
Bonus: Free parking