You can make it short like half hour if you are not interested in taking a lot of pictures! But if you like taking pictures it could take 2 hours.
1-2 hrs depends on how long you linger
Weekdays are not as busy. Weekends you'll wait at each station behind others
If you are taking pictures, it could take even more than 2 hours :D I just had a lot of fun doing that with a friend of mine.
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