King of Thorns by Mark Lawrence

“Wossit?” Gog stared entranced.
“The Builders made it,” I said. “It’s a thousand years old.”
Row and Red Kent came over to see.
 “I’m told they call it a watch,” I said. “And you can see why.”
In truth, I’d been watching it a lot myself. It had a face on it behind crystal, with twelve hours marked and sixty minutes, and two black arms that moved, one slow, one slower still, to point out the time. Entranced, I had opened it up at the back with the point of my knife and gazed into the guts of the thing. The hatch popped back on a minute hinge as if the Builders had known I would want to see inside. Wheels within wheels, tiny, toothed, and turning. How they made such things so small and so precise I cannot guess but to me it is a wonder past any man-made sun or glow-light.