A view of the Prince Edward Viaduct from the east bank of the Don River
The Prince Edward Viaduct was built in 1913, at a cost of nearly $2.5 million (which would be $33 million today). One really interesting thing about it is that the designer, Edmund W. Burke, and Toronto's then Commissioner of Public Works, R.C. Harris, insisted on including a lower level, below the road surface, which could eventually accommodate a rail line, even though it added thousands to the cost and Toronto had no such railway at the time. When the Bloor-Danforth line of the subway was eventually built, this structure made its construction much easier and less expensive.
The Don's watershed flows more than thirty kilometres from the Oak Ridges Moraine, north of Toronto, south to its end at Keating Channel in Lake Ontario. There is no one uninterrupted trail along the river, but there are many great walking and biking paths, which can be enjoyed by people of varying physical abilities.
There are nine Discover Walks through various parts of Toronto, including along the Don and around surrounding neighbourhoods. The area of the Don between Pottery Road and Gerrard Street is called the Ravines Reach because three creeks, each with an associated ravine, flow into the river here. You can find lots more fascinating information, including maps, at lostrivers.ca