The new Ontario Line subway under construction in Toronto will include many individual achievements that will collectively form the 15-stop, 15.6-km transit line connecting Exhibition Place with the recently-shuttered Ontario Science Centre.

This includes the first subway tunnel that will be constructed through downtown Toronto in over six decades, as well as the first significant new elevated crossing of the Don River Valley built in almost a century.

A recent Metrolinx blog post outlines plans for three "landmark" bridges planned as part of the Ontario Line, which the transit agency promises "will transform the cityscape."

The flashiest of the bunch will be the Lower Don Bridge, which will cross the Don River in the West Don Lands and Riverside neighbourhoods with a steel network tied arch structure, allowing a clear span over both the river and adjacent DVP, with no piers required in the river or on the highway.

However, it will be the two Don Valley bridges, which will carry trains across the Don Valley in the north segment of the Ontario Line, that will truly stand out with their sheer scale.

The future Don Valley Crossing Bridge will rise as high as 38 metres above the valley floor at its highest point with a balanced cantilever design, becoming the first high-level crossing of the valley constructed since the Leaside Bridge was built in 1927.

It will be joined by a second bridge spanning the West Don, which will feature the same construction method, linking separate guideways serving the Thorncliffe Park and Flemingdon Park stations.

John Potter, senior manager subways sponsor at Metrolinx, was quoted as saying that the transit agency "wanted something very slender and elegant, like ribbons crossing the valley."

"We aimed to minimize the visual clutter that often mars the beauty of civic structures. For example, we have integrated the downspouts into the piers, so that it does not appear tacked on."

Potter says that the resulting minimalist designs frame "the valley itself is the feature."