The Peterborough Lift Lock is the world’s highest hydraulic lift lock. Opened in 1904, it was an engineering marvel in its day. It was the largest single pour of unreinforced concrete as the use of rebar was not common practice in 1904. It is still an impressive structure. As one approaches from the east, it is an awesome sight ahead. We had ridden our bikes over to watch it work prior to locking through ourselves. A hydraulic lift lock works like a simple balance scale. A boat enters a huge pool.
Parallel to this pool is another, a twin, 65 feet higher on a large piston.
Once the boats enter, a gate is raised behind them. 
The water in each pool weighs 1.500 tons. When the upper pool is filled with an additional one foot of water (130 tons), the increased weight forces it, boats and all, to descend on its piston forcing the lower pool to ascend. 
It is an incredible ride! 
This is one of the highlights of our trip so far and there have been many!
