Cave of the Winds, Niagara Falls (about $20 / ticket, depending on age and time of year), recommended, but only if you can do stairs, because it’s basically all stairs after the museum part.
It’s a timed entry event, so there aren’t ever too many people out there at once, and while you’re waiting, they do a nice job of giving you a little educational museum to wander through for ten minutes, talking about the history of the falls…
….and for Nikola Tesla fans (and boy, does it irritate me that now I can’t talk about Nikola without also thinking of Musk, dammit), a good explanation of the battle between Nikola and Edison for production of power in America.
“The Serbian-American scientist was a brilliant and eccentric genius whose inventions enabled modern-day power and mass communication systems.
His nemesis and former boss, Thomas Edison, was the iconic American inventor of the light bulb, the phonograph and the moving picture. The two feuding geniuses waged a “War of Currents” in the 1880s over whose electrical system would power the world — Tesla’s alternating-current (AC) system or Edison’s rival direct-current (DC) electric power.”