2-3 hours typically.
You need to block time slot while ticket booking. It depends on queue. In every 30 minutes there is time slot. Reach to entrance queue in 15-20 minutes in advance. Need at least 2 hours to complete the tour on top. They give 2 tour per ticket per day. Day time and night time. I suggest, if you are planning for sight seeing Seattle. First and last thing you plann for space needle.
You can take as long a you like. There is lots to see. Just don't go before closing everyone gets in a hurry to get you out of there.
We spent approximately 2 hours. Depends on the crowd & your patience!
Suggest to make 2hrs for your stay, including sightseeing and a cup of coffee at the top, plus window shopping in the gift shop. There is also a glass museum and a center house for your tour If you can extend your stay.
It depends how much time you spend in taking photos :) after reaching at top. But 30-45 minutes are sufficient to enjoy the city beauty from space Needle.
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