The Rat Hole was a 2-lane tunnel constructed in 1927 and traversed north-south under present day 109th Street between 104th and 105th Avenue. It was 168 metres in length, 3.3 metres in height, and constructed to accommodate automobile, bicycle and pedestrian traffic to cross under 22 railway tracks in the old Canadian National Railway yards that ran along the north side of 104 Avenue.
The 109 Street Subway, the original name of the tunnel, was officially opened by then Mayor Ambrose Bury on October 19, 1928. An Edmonton alderman later coined the name “Rathole” for the tunnel.
In 1957, a transportation study recommended the construction of a parallel subway to improve the traffic flow. However, in lieu of this recommendation, in 1960 the city constructed an overpass along 105th Street over the CN rail tracks.
The tunnel was susceptible to seasonal flooding, and proved hazardous because of its low clearance and visibility upon entrance and exit. There were also safety issues concerning pedestrian usage of the tunnel. The tunnel remained opened for 73 years, during which, as many as 27,000 cars passed through daily.
The project began in April 2000. The project was completed 3 weeks ahead of schedule on July 4, 2000. This was accomplished by beginning demolition of the tunnel from the north end instead of taking the entire tunnel out at once. Concrete removed from the tunnel was recycled and used in the fill.
From Wikipedia: http://en.wikipedia.org/wiki/Rat_Hole
This picture shows the Rat Hole. The only thing recognizable in this picture is the building on the right, The Dorchester.
This YouTube video shows events the last day it was open: https://www.youtube.com/watch?v=DS5YH0Hngi0