If you are planning to visit Nainital and do NOT have a pre-booked accommodation, it is strongly advised to take Ranikhet Express instead of Shatabdi Express.
The reason is that the check-out time of most hotels is 10:00 AM and getting a room at decent tariffs is easier if you reach by 9 AM or something.
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Apart from this, by reaching...
more... early you can avoid the traffic on the highway. Else the insignificant Kathgodam-Nainital distance can eat up 2-3 hours in the noon.