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At Great Falls Tavern Visitor Center you can take a ride on a canal boat.  They move the boat into the lock by mule, raise the level of the water like they did in the 1800s and the mules pull it down the canal.  Canal boats don't have to turn around, being pointed at both ends, so mules just turn around and bring the boat back to the lock where it is lowered and back to where the dock is to load and unload people.
The falls are located here and you can see the falls from the bank of the river near the center.  I cycled the towpath 15 miles into Washington DC where I caught a bike trail to the Lincoln Memorial.  I cycled around the mall to the Jefferson Memorial, WWII Memorial, and the FDR Memorial. I cycled back up the towpath to Great Falls, a total of 40 miles.