Generally speaking, tickets to scenic spots are valid on the same day unless otherwise stated.
Gubeikou is in Miyun, Beijing: the surrounding Great Wall is Simatai Great Wall. It is a different scenic spot from Jinshanling Great Wall: tickets are not universal.
Although the Simatai Great Wall in Gubei Water Town is right in front of you when looking north to the Jinshanling Great Wall, the sections open as scenic spots are not connected.
The section of the lowest “No. 1 (Beacon) Tower” in the Simatai Great Wall Scenic Area toward Jinshanling has collapsed and been disconnected; it is also blocked by a river and cannot be reached on foot.
If you drive around, the distance from Beijing Miyun to
Chengde
Luanping

It is 25km and takes half an hour.

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