The Main Street Tunnel carries Niagara Road 27 under the Welland Canal — rather than a bridge that interrupts ship traffic, the tunnel was the practical solution on the eastern side of the canal crossing. Completed in 1973, it is a subaqueous tunnel bored under the canal floor, about 330 metres long including the approaches. It is not a tourist attraction in the traditional sense, but driving or cycling through it gives a tangible sense of the engineering challenges the canal creates for the surrounding road network.
For visitors trying to understand how a city manages to have an ocean shipping lane running through its center, the tunnel is a concrete piece of that answer. The Townline Tunnel to the south is the only other such tunnel on the Welland Canal.