In the show Game of Thrones there is this thing called The Wall. It is a monstrous, 300 mile (≈ 483 km) long bulwark consisting of a fortified ice wall that is 700 feet (≈ 213 meters) high (check the wiki for more details). There are also castles/forts along the foot of this wall, as garrisons for the soldiers manning it.
Now, quite conveniently, at some of the castles there exists a sort of elevator built to reach the battlements from the castle 700 feet below the top of the wall. We can see the elevator is built from wood and metal and seems to be a fairly simple construction. No actual mechanism is shown. At the bottom is a lever, that when turned either sends the elevator cabin up or down respectively.
Given world like the one presented in Game of Thrones—What could be used to power the elevator?
- No magic
- The tech level is that of an (at most) late-medieval'ish civilisation
- Should work in the cold weather required to preserve an ice wall
- Works with as little work from people and or animals as needed.
- Can be operated by some sort of lever or switch (either at the top or bottom)
- Maintenance needs should be as low as feasible
Note: I'm aware there might be a canon answer in the books (though I don't remember anything too specific). That is not what I'm asking for, and this would be the wrong Stackexchange to do so anyway. I'm wondering for general reality-based solutions for this problem outside of the actual Game of Thrones context.