Here's an unusual one, it's a card model of a giant sundial, built on an architectural scale, in New Delhi, India. The original was built in the early 1700's as part of the Jantar Mantar Royal Observatory. The gnomon that casts the shadow is some 70 feet high, so a high precision of timekeeping is possible, theoretically to some 2 seconds.
Paper Models | Jantar Mantar
The instructions provide a useful section on using the model as a sundial, with the necessary adjustments for latitude.
A fascinating historic observatory, some of the other instruments are amazing to look at.
Julian