It all depends on you, and the age of children who are with you. If you do the interactive games and projects, and if this is your first time, I'd give it 4 hours, not including breaks and lunch. The Lego area alone can take an hour for kids who like building.
There are a lot of Interactive displays. My kids, aged 4 through 9, were actively engaged for about three hours. We also watched an IMAX movie there about architecture and engineering. All in all, you can easily spend 3 to 4 hours.
I guess whether or not your kids play in the Lego area will make a big different. My 4 and 5 year old spent 2 hours here. They skipped the Lego area and I'm VERY grateful they weren't interested in that because they have legos at home and I wasnt spending money just so they can do something they already can do at home..Besides skipping that area, they saw everything else in 2 hours. They DID want to revisit some of the exhibits, but we finished just as they were closing. If they hadn't closed and we HAD revisitied some of the exhibits they wanted, we might have spent another half hour or so. I cant imagine it being more than that because they basically just wanted to play in the ball pit, and the labyrinth a couple more times.
2 to 3 hours without a movie. Add an hour if you watch a movie.
I agree that it depends on how many movies you want to watch...there is a second film in a smaller viewing room Or you may watch 2 IMAX. Then the museum part can take a couple of hours to do all of the activities...and those change periodically depending on theme but some things stay too. I suggest taking the time to plan a whole day around it and adding in eating a picnic lunch by the fountain. enyoy this museum.
It depends if your gonna watch a movie or not museum only 1.5 hours, museum and movie 3.0 hours.
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