We're used to water being a changing, fluttering thing, flowing into ripples around rock obstructions and pulled into ribbon veils by the wind. Niagara is a solid sheet of greenish water, shell-curved, like worked glass, thick and glossy and shimmering, solid. No obvious movement. I thought it was a very impressive geological feature - craggy cliffs cut and crumbled over thousands of years, a plume of mist visible from miles away - but not really a waterfall.
But at night they turn on lights - scarlet and indigo and shimmering green and blue projected onto the murmuring glassine shell of the falls. The lights drift and shimmer in the mist and play in darts and ripples in the falls themselves. At night, at least, with the wind blowing mist into your face and the lights bringing movement to the falls, Niagara is a real waterfall.