I've been to the Niagara Falls and they are most impressive, take away the water and what have you got? A cliff. That said, the Falls without water still makes for some impressive viewing.
Russ Glasson recently stumbled across these pictures, which were taken by his in-laws, and had been left in an old shoebox in their garage for over four decades. 
Mr Glasson said: 'My in-laws took these pictures during the six months through June to November that the Army was working to improve the health of the American Falls.'
In June 1969, U.S. engineers diverted the flow of the Niagara River away from the American side of the falls for several months.

The riverbed was studied, mechanically bolted and a number of faults strengthened to delay the gradual erosion of the American Falls.

Engineers constructed a dam up river stopping the water for the first time in 12,000 years.

Two rock slides from the plate of the falls in 1931 and 1954 had caused a large amount of rock to be collected at the base.

You can see the temporary dam in the top of this pic

back flowing again