Falkirk Wheel, Scotland, United Kingdom

If it were not for inclusion of the docking-pit the caissons and extremities of the arms of the wheel would be immersed in water at the lower canal basin each time the wheel rotates. This would result in a number of undesirable situations developing, such as providing buoyancy to the bottom caisson and the viscosity of the water causing an increase in the required power.
How the canal was routed through the wheel
The route chosen to take the Union Canal to the site of the wheel involved building a completely new section of canal, leading from the original terminus at Port Maxwell to link up with a new basin to the south of the wheel.
The water level in this basin is the same as the aqueduct at the top section of the wheel, the two being joined by the new 150 metre long Rough Castle Tunnel with elliptical cross section. This is the most recent new canal tunnel to be built in the UK since canal excavation in Dudley, West Midlands.