Eiffel's Funicular Wheel

The "elevators" that run from the ground to the first and second levels are more appropriately called funicular railways. They travel up and down on steeply-sloped railroad rails, and they're moved by hydraulic winches. Wheels like this one sit every 20 feet or so to keep the winch cables more or less parallel to the rails. They spin freely when the cables move, and after the lift car passes by, they don't move until the car comes back down and puts the cable back onto the wheel's guide surface.